i965: Handle lum, intensity and missing components in the fast clear

i965: Handle lum, intensity and missing components in the fast clear

It looks like the sampler hardware doesn't take into account the
surface format when sampling a cleared color after a fast clear has
been done. So for example if you clear a GL_RED surface to 1,1,1,1
then the sampling instructions will return 1,1,1,1 instead of 1,0,0,1.
This patch makes it override the color that is programmed in the
surface state in order to swizzle for luminance and intensity as well
as overriding the missing components.

Fixes the ext_framebuffer_multisample-fast-clear Piglit test.

v2: Handle luminance and intensity formats
Reviewed-by: Ben Widawsky <benjamin.widawsky@intel.com>