armv7: fix relocation skip

I doubt the stack_setup() was defective before:
 we load the current location of _start and compare against destination
 of relocate_code(). If we are already there we shoud skip the
 relocation and jump over to clear_bss. Before the clear_bss was also skipped.

Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>