gallium: Fix big-endian addressing of non-bitmask array formats.

gallium: Fix big-endian addressing of non-bitmask array formats.

The formats affected are:

- LA x (16_FLOAT, 32_FLOAT, 32_UINT, 32_SINT)
- R8G8B8 x (UNORM, SNORM, SRGB, USCALED, SSCALED, UINT, SINT)
- RG/RGB/RGBA x (64_FLOAT, 32_FLOAT, 16_FLOAT, 32_UNORM, 32_SNORM,
                 32_USCALED, 32_SSCALED, 32_FIXED, 32_UINT, 32_SINT)
- RGB/RGBA x (16_UNORM, 16_SNORM, 16_USCALED, 16_SSCALED,
              16_UINT, 16_SINT)
- RGBx16 x (UNORM, SNORM, FLOAT, UINT, SINT)
- RGBx32 x (FLOAT, UINT, SINT)
- RA x (16_FLOAT, 32_FLOAT, 32_UINT, 32_SINT)

The updated st_formats.c unit test checks that the formats affected by
this change are all array formats in the equivalent Mesa format (if
any).  Mesa's array format definition is clear: the value stored is an
array (increasing memory address) of values of the channel's type.
It's also the only thing that makes sense for the RGB types, or very
large types like RGBA64_FLOAT (A should not move to the low address
because the cpu is BE).

Acked-by: Roland Scheidegger <sroland@vmware.com>
Acked-by: Adam Jackson <ajax@redhat.com>
Tested-by: Matt Turner <mattst88@gmail.com> (unit tests on BE)
Reviewed-by: Marek Olšák <marek.olsak@amd.com>