pan/mdg: Keep min_bound at 16 when alignment requires it

Otherwise LCRA will try to divide by zero when calculating m_max.

Fixes: 553c2cf16b ("pan/mdg: Set RA bounds for fp16")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16382>
(cherry picked from commit b1ecb90941)

.pick_status.json

@@ -697,7 +697,7 @@
         "description": "pan/mdg: Keep min_bound at 16 when alignment requires it",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "553c2cf16b7612d4a70bd96230dad63777ec867e"
     },

src/panfrost/midgard/midgard_ra.c

@@ -543,7 +543,7 @@ allocate_registers(compiler_context *ctx, bool *spilled)
                         3; /* 8-bit todo */
 
                 /* We can't cross xy/zw boundaries. TODO: vec8 can */
-                if (size == 16)
+                if (size == 16 && min_alignment[dest] != 4)
                         min_bound[dest] = 8;
 
                 mir_foreach_src(ins, s) {