panfrost: Permit AFBC of RGB8

Ugly but hey.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5284>
diff --git a/src/panfrost/encoder/pan_afbc.c b/src/panfrost/encoder/pan_afbc.c
index 26ba748..27dacab 100644
--- a/src/panfrost/encoder/pan_afbc.c
+++ b/src/panfrost/encoder/pan_afbc.c
@@ -92,6 +92,10 @@
         if (util_format_is_rgba8_variant(desc))
                 return true;
 
+        /* Gross, but probably good enough */
+        if (format == PIPE_FORMAT_R8G8B8_UNORM)
+                return true;
+
         /* Only Z24S8 variants are compressible as Z/S */
 
         if (panfrost_is_z24s8_variant(format))