intel: Enable blit glCopyTexSubImage/glBlitFramebuffer with sRGB.

intel: Enable blit glCopyTexSubImage/glBlitFramebuffer with sRGB.

Since the introduction of default-to-SARGB8 window system framebuffers,
non-blorp hardware lost blit acceleration for these two paths between the
window system and ARGB8888 textures.  Since we shouldn't be doing any
conversion anyway, just compatibility-check the linear variants of the
formats.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=61954
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Tested-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>