libmix: optimize getbits, peekbits, skipbits

BZ: 189364

use 32 bits cache in getbits,peekbits function
to avoid multiple loading byte operation

Change-Id: I0bf1758d6f6b0eca9d03075778fc550d87af206a
Signed-off-by: ywan171 <yi.a.wang@intel.com>
6 files changed