panfrost: assert(0) -> unreachable for some switch

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
diff --git a/src/gallium/drivers/panfrost/pan_format.c b/src/gallium/drivers/panfrost/pan_format.c
index a61d7b1..5f75a06 100644
--- a/src/gallium/drivers/panfrost/pan_format.c
+++ b/src/gallium/drivers/panfrost/pan_format.c
@@ -53,8 +53,7 @@
                 return MALI_CHANNEL_ONE;
 
         default:
-                assert(0);
-                return 0;
+                unreachable("INvalid swizzle");
         }
 }
 
@@ -100,9 +99,7 @@
                 case 32:
                         return MALI_CHANNEL_32;
                 default:
-                        fprintf(stderr, "Unknown width %d\n", size);
-                        assert(0);
-                        return 0;
+                        unreachable("Invalid width");
         }
 }
 
@@ -128,8 +125,7 @@
                         }
 
                 default:
-                        assert(0);
-                        return 0;
+                        unreachable("Invalid type");
         }
 }
 
@@ -232,9 +228,7 @@
                         break;
 
                 default:
-                        fprintf(stderr, "Unknown format type in %s\n", desc->name);
-                        assert(0);
-                        break;
+                        unreachable("Invalid format type");
         }
 
         return (enum mali_format) format;