The 64 bit version of ARGBToRGB565 to 32 bit. 64 bit is using sri which shifts and inserts, saving some masking.  The instruction is available for neon 32 bit as well.

R=magjed@chromium.org, harryjin@google.com
BUG=libyuv:571

Review URL: https://codereview.chromium.org/1724393002 .