Dear Venkatesh,
if you would like to go for EHP7 then you have to ensure that your OS/DB combination is supported with that release.
Please check the Product Availability Matrix on below URL:
Depending on the target release support package level (SAP_BASIS 740) you have to choose your kernel level. Please check note #1969546 (Release Roadmap Kernel 740) for more information.
Finally you have to upgrade your OS and DB before performing the upgrade. Although the OS/DB combination will not be supported for productive use, it will be supported for upgrade purposes.
Best regards,
Andreas