anv/formats: Fix build on gcc-4 and earlier

anv/formats: Fix build on gcc-4 and earlier

gcc-4 and earlier don't allow compound literals where a constant
is required in -std=c99/gnu99 mode, so we can't use ISL_SWIZZLE()
when populating the anv_formats[] array. There are a few ways around
it: First one would be -std=c89/gnu89, but the rest of the code
depends on c99 so it's not really an option. The second option
would be to upgrade to gcc-5+ where the compiler behaviour was relaxed
a bit [1]. And the third option is just to avoid using compound
literals. I chose the last option since it keeps gcc-4 and earlier
working.

[1] https://gcc.gnu.org/gcc-5/porting_to.html

Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: Topi Pohjolainen <topi.pohjolainen@intel.com>
Fixes: 7ddb21708c80 ("intel/isl: Add an isl_swizzle structure and use it for isl_view swizzles")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>