x86: move misplaced rodata check call

It looks like a mismerge put the rodata self-check in the wrong spot; move
it to the right place after marking the .rodata section read only.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>