x86: move MWAIT idle check to generic CPU initialization on 32-bit

Previously it was only run for Intel CPUs, but AMD Fam10h implements MWAIT too.

This matches 64bit behaviour.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>