Align a buffer for simd operation
Align a buffer for simd operation

BUG=aomedia:387

Change-Id: I11fdc9dbc4b0f4484e82ab1662ac329b8b7f2d6c

smarter/aom,luctrudeau/aom,smarter/aom,GrokImageCompression/aom,GrokImageCompression/aom,luctrudeau/aom,GrokImageCompression/aom,luctrudeau/aom,GrokImageCompression/aom,smarter/aom,luctrudeau/aom,GrokImageCompression/aom,smarter/aom,luctrudeau/aom,smarter/aom,GrokImageCompression/aom,smarter/aom,luctrudeau/aom