i965/gen9: Support fast clears for 32b float

i965/gen9: Support fast clears for 32b float

SKL supports the ability to do fast clears and resolves of 32b RGBA as both
integer and floats. This patch only enables float color clears because we
haven't yet enabled integer color clears, (HW support for that was added in
BDW).

v2: Remove LUMINANCE16F and INTENSITY16F special cases since they are now
handled by Neil's patch to disable MSAA fast clears.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Neil Roberts <neil@linux.intel.com>
Reviewed-by: Chad Versace <chad.versace@intel.com>