pvr: Add support for sampler border colors

Currently only the six vulkan 1.0 pre-defined formats are supported, but some basic infrastructure that will be useful for implementing VK_EXT_custom_border_color (and vulkan 1.1) is included.

Only formats currently listed in the pvr_format_table in pvr_formats.c are currently supported. Unlike most (all?) other drivers, the PowerVR hardware requires each entry in the border color table to be encoded for every hardware format (of which there are 128 available, plus 128 for compressed formats).

Also in this commit:

• Two new constants in rogue_texstate.xml:
  • IMAGE_WORD0_TEXFORMAT_MAX_SIZE, and
  • SAMPLER_BORDERCOLOR_INDEX_MAX_SIZE; and
• A new device feature (tpu_border_colour_enhanced)

Signed-off-by: Matt Coster <matt.coster@imgtec.com>
Reviewed-by: Karmjit Mahil <Karmjit.Mahil@imgtec.com>