FIELD OF INVENTION The invention relates to a high strength hot rolled dual phase steel sheet with a minimum tensile strength of 800 MPa. Particularly the invention relates to method of manufacturing the hot rolled dual phase steel sheet. BACKGROUND Self-weight of trucks is increasing with increase in load capacity of trucks. There is a need to increase in load capacity by weight reduction of the truck to reduce the transportation cost and cost of the truck and hence reduce the air pollution. The weight reduction of truck body can be decreased by using advanced high strength steel sheet to body. Especially, the application to long members of truck frame is important because of its high weight in overall weight of the body. From the point of view of application of truck body, the most important functional requirement is high strength with good amount of ductility. There is a trend towards the use of hot rolled sheets of a minimum tensile strength of 800 MPa for long members of the truck body. US20040118489A1 discloses a method in which a hot rolled dual phase steel sheet is subjected to cooling and coiling above 450oC so as to achieve a yield strength varying in the range of 500 to 900 MPa. However, coiling above 450oC will lead to tempering of martensite and precipitation of carbides. This will results in non-uniform properties in the coil as there will be a large variation in temperature across the coil. US2011146850 discloses a method of producing a hot rolled dual phase steel sheet with a microstructure consisting of ferrite, martensite, bainite and austenite and ferrite. Addition of carbide forming elements such as Nb, Ti, V are required besides considerable amount of C and N to achieve a tensile strength 500 -1000 MPa. However, this steel will become expensive due to addition of carbide forming elements and also close monitoring is required to control Nitrogen content in the steel during steel making process. JP10280096A discloses a method of producing a high-strength hot-rolled dual phase steel sheet of tensile strength greater than 780 MPa through conventional hot rolling processes. High rate of cooling, as much as 100°C/sec is required during last of stage of cooling on RoT for the development of the product. This targe cooling rate may not be feasible always In plant conditions and may lead to non-uniform properties along the strip, OBJECTIVES OF THE INVENTION In view of the foregoing limitations inherent In the prior-art, it is an object of the invention to develop a hot rollec dual phase (HRDP) steel, which comprises uniform properties in the coil, considerably inexpensive. Another object of the invention is the strength of the steel lies in the range of 800 -1126 MPa. Still another object of the invention is that the close monitoring to be not required to control Nitrogen content in the steel during steel making process. SUMMARY OF THE INVENTION In one aspect, the invention provides a process for making a hot rolled dual phase (HRDP) steel comprising steps of: casting a steel with composition 0.06- 0.08 of carbon (C), 1.0-1.5 of manganese (Mn), 0.5-0.7 of silicon (Si), 0 - 0.32 chromium (Cr), 0.10 - 0.22 Molybdenum (Mo), maximum 0.005 of sulphur (S), maximum 0.030 of phosphorus (P), maximum 0.005 of nitrogen (N), rest iron (Fe) and incidental ingredients (all in wt. percentage); finish rolling the steel at temperature T1, (A3 + 50°C) < T1 < (A3 + 70°C); air cooling the steel till it attains temperature T2, (T1 - 15)°C