x86-64, asm: Directly access per-cpu IST
x86-64, asm: Directly access per-cpu IST

Use a direct per-cpu reference for the IST instead of using a scratch
register.

Signed-off-by: Brian Gerst <e60badcb99f652a0bcc15460d39f7ea12d6655ee@gmail.com>
LKML-Reference: <1280594903-6341-1-git-send-email-e60badcb99f652a0bcc15460d39f7ea12d6655ee@gmail.com>
Signed-off-by: H. Peter Anvin <8a453bad9912ffe59bc0f0b8abe03df9be19379e@zytor.com>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs