Revert "i965: Use MESA_FORMAT_B8G8R8X8_SRGB for RGB visuals"

Revert "i965: Use MESA_FORMAT_B8G8R8X8_SRGB for RGB visuals"

This reverts commit 839793680f99b8387bee9489733d5071c10f3ace.

The patch was breaking DRI3 because driGLFormatToImageFormat does not
handle MESA_FORMAT_B8G8R8X8_SRGB which ended up making it fail to
create the renderbuffer and it would later crash. It's not trivial to
add this format because there is no __DRI_IMAGE_FORMAT nor
__DRI_IMAGE_FOURCC define for the format either. I'm not sure how
difficult adding this would be and whether adding a new format would
require some sort of new version for DRI. Seeing as this might take a
while to fix I think it makes sense to just revert the patch in the
meantime in order to avoid regressing master.

It is also not handled in intel_gles3_srgb_workaround and there may be
other cases where it breaks.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93388
Acked-by: Jason Ekstrand <jason.ekstrand@intel.com>