Two skia optimizations:

1. Combine S16_opaque_D32_nofilter_DX and clampx_nofilter_trans
2. Change MAX_BUF between mproc and sproc to 1024 from 128

Opt 1 is giving about 8-10 FPS in gmail and facebook apk.
Opt 2 is helping all combinations for shaderspan.

Change-Id: I88dc097ffd52984a7b786e13c70384688f2e1b12