samsung-i9003: Change armhf to armv7 and heimdall-isorec to heimdall-bootimg

I noticed that the Samsung i9003 is actually a heimdall-bootimg device. But at the same time, the kernel is assembled as if it is isorec. I built the kernel in a standard way and did not see a difference in the size of vmlinuz nor in the behavior of its work.

• Changed armhf to armv7