i965: Fix I/L/LA SNORM formats.
_mesa_choose_tex_format (texformat.c) tries I8_SNORM, L8_SNORM, and
either L8A8_SNORM or A8L8_SNORM, none of which are supported by our
driver. Failing that, it falls back to RGBX for luminance, and RGBA
intensity and luminance alpha. So, we need to use swizzle overrrides
to obtain the correct values.
Fixes Piglit's EXT_texture_snorm/fbo-blending-formats and
fbo-clear-formats.
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>
Reviewed-by: Chris Forbes <chrisf@ijw.co.nz>