i965: Drop the "do resolves in sRGB" hack.

i965: Drop the "do resolves in sRGB" hack.

I've never quite understood the purpose of this hack - supposedly,
doing resolves in the sRGB colorspace is slightly more accurate.

Currently, BlitFramebuffer() ignores sRGB encoding and decoding
on OpenGL, although it encodes and decodes in GLES 3.x.

The updated OpenGL 4.4 rules also allow for encoding and decoding
if GL_FRAMEBUFFER_SRGB is enabled, allowing the application to
control what colorspace blits are done in.  I don't think this hack
makes any sense in such a world - the application can do what it
wants, and we shouldn't second guess them.

A related Piglit patch, "Make multisample accuracy test set
GL_FRAMEBUFFER_SRGB when resolving." makes the Piglit MSAA accuracy
test explicitly request SRGB encoding/decoding during resolves when
running "srgb" subtests.  Without that patch, this commit will regress
those tests, but with it, they should continue to work just fine.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>