i965/chv|skl: Apply sampler bypass w/a

i965/chv|skl: Apply sampler bypass w/a

Certain compressed formats require this setting. The docs don't go into much
detail as to why it's needed exactly.

This patch introduces no piglit regressions on gen9 (bsw is untested). Note that
the SKL "regressions" are fixed tests, and the egl_khr_gl_colorspace tests are
WTF. The patch also fixes nothing I can find.
http://otc-mesa-ci.jf.intel.com/job/Leeroy/127820/

v2:
Reworded commit message (Matt); Added piglit results link.
Restructured condition (Matt)
Moved check out to function (Nanley). I left the setting of the bit in the
  surface state open coded because it seems to go better with the existing code.

v3:
Use and inline function only in gen8_emit_texture_surface_state() (Matt).

Cc: Matt Turner <mattst88@gmail.com>
Cc: Nanley Chery <nanleychery@gmail.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Matt Turner <mattst88@gmail.com>