util/format: Add new 12-bit P012 RGB/planar formats

Introduce three 12-bit formats: X4R12_UNORM, X4R12X4G12_UNORM, and X4G12_X4B12X4R12_420_UNORM.
These formats allocate 12 bits for each color channel with 4 bits of padding to align with Vulkan's P012
and related planar formats.

Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Signed-off-by: Valentine Burley <valentine.burley@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30821>

src/util/format/u_format.yaml

@@ -1902,7 +1902,7 @@
   swizzles: [X, 0, 0, 1]
 
 
-# RGB versions of NV12, YV12, and P010 for hardware that supports sampling
+# RGB versions of NV12, YV12, P010, and P012 for hardware that supports sampling
 # from multiplane textures but needs color-space conversion in the shader.
 - name: R8_G8B8_420_UNORM
   layout: planar2
@@ -1952,6 +1952,12 @@
   block: {width: 1, height: 1, depth: 1}
   channels: [X6, UN10]
   swizzles: [X, Y, Z, W]
+- name: X4G12_X4B12X4R12_420_UNORM
+  layout: planar2
+  colorspace: RGB
+  block: {width: 1, height: 1, depth: 1}
+  channels: [X4, UN12]
+  swizzles: [X, Y, Z, W]
 
 # While most of Mesa uses R8 for Y, U, and V planes, freedreno requires
 # distinguishing between tiled Y8 data and tiled R8 data.
@@ -1976,6 +1982,21 @@
   channels: [X6, UN10, X6, UN10]
   swizzles: [Y, W, 0, 1]
 
+# Formats for plane 0/plane 1 of P012
+- name: X4R12_UNORM
+  layout: plain
+  colorspace: RGB
+  block: {width: 1, height: 1, depth: 1}
+  channels: [X4, UN12]
+  swizzles: [Y, 0, 0, 1]
+- name: X4R12X4G12_UNORM
+  layout: plain
+  colorspace: RGB
+  block: {width: 1, height: 1, depth: 1}
+  channels: [X4, UN12, X4, UN12]
+  swizzles: [Y, W, 0, 1]
+
+
 - name: Y8_U8_V8_422_UNORM
   layout: planar3
   colorspace: YUV