x86/cpufeature: Cleanup get_cpu_cap()

Add an enum for the ->x86_capability array indices and cleanup
get_cpu_cap() by killing some redundant local vars.

Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1449481182-27541-3-git-send-email-bp@alien8.de


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>