x86: move to .rodata/.init.data

The array is never written, and on 64-bits it's not even being used
past initial boot.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>