This fixes an issue with context clearing introduced by commit
5e81643d.

In av1_zero_above_context width_y went from being assigned "2 *
aligned_width" to "width << 1". All this patch does is replace width
with the aligned_width.

This resolves an issue with random resizing being broken on the master
branch.

Change-Id: Ib60bf81e6091802053a5a26057c626d4efe6497c