i965/gen9: Configure rbc buffers as plain for non-rbc tex views

i965/gen9: Configure rbc buffers as plain for non-rbc tex views

Fixes rendering in Shadow of Mordor with rbc. Application writes
RGBA_UNORM texture filling it with values the application wants to
later on treat as SRGB_ALPHA.
Intel driver enables lossless compression for the buffer by the time
of writing. However, the driver fails to make sure the buffer can be
sampled as something else later on and unfortunately there is
restriction in the hardware for using lossless compression for srgb
formats which looks to extend itself to the sampling engine also.
Requesting srgb to linear conversion on top of compressed buffer
results the color values to be pretty much garbage.

Fortunately none of tracked benchmarks showed a regression with
this.

v2 (Matt): Add missing space

Cc: "12.0" <mesa-stable@lists.freedesktop.org>
Signed-off-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>