util/format: Add G8_B8R8_420_UNORM to match Vulkan.

turnip was playing fast and loose with the name, using the R8_G8B8 format
name but actually setting the descriptors up to read G8_B8R8 like Vulkan
(sensibly) wants.  This caused trouble when trying to make freedreno and
turnip share code.  By having both orderings as format names, we can share
the descriptor code and also confuse readers less.

Reviewed-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13443>

src/util/format/u_format.csv

@@ -400,6 +400,7 @@ PIPE_FORMAT_NV21                  , planar2, 1, 1, 1,     ,     ,     ,     , xy
 # RGB version of NV12 and YV12 for hardware that supports sampling from
 # multiplane textures but needs color-space conversion in the shader.
 PIPE_FORMAT_R8_G8B8_420_UNORM     , planar2, 1, 1, 1,  un8,     ,     ,     , xyzw, rgb
+PIPE_FORMAT_G8_B8R8_420_UNORM     , planar2, 1, 1, 1,  un8,     ,     ,     , xyzw, rgb
 PIPE_FORMAT_G8_B8_R8_420_UNORM    , planar3, 1, 1, 1,  un8,     ,     ,     , xyzw, rgb
 
 # While most of Mesa uses R8 for Y, U, and V planes, freedreno requires distinguishing

src/util/format/u_format_table.py

@@ -109,6 +109,7 @@ def has_access(format):
         'y16_u16v16_422_unorm',
         'y16_u16_v16_444_unorm',
         'r8_g8b8_420_unorm',
+        'g8_b8r8_420_unorm',
         'g8_b8_r8_420_unorm',
         'y8_unorm',
     ]