use hardware acceleration for keyguard

Without hardware acceleration, keyguard widget will appear aliased
and choppy (especially at the end of the scroll).

Change-Id: I1bfb6fbcba6306edf366e8ea752d6919936c3ab6
credit: Pawit Pornkitprasan
Merge pull request #5 from ToxicThunder/patch-2

use hardware acceleration for keyguard