mm/page_alloc.c: simplify calculation of combined index of adjacent buddy lists
mm/page_alloc.c: simplify calculation of combined index of adjacent buddy lists

The previous approach of calucation of combined index was

	page_idx & ~(1 << order))

but we have same result with

	page_idx & buddy_idx

This reduces instructions slightly as well as enhances readability.

[5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org: coding-style fixes]
[5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org: fix used-unintialised warning]
Signed-off-by: KyongHo Cho <85e547a6ca510a81af12a94f261b0997900ebcc5@samsung.com>
Signed-off-by: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

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