lima: Fix uninitialized var warning from using assert() as unreachable().

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6462>

src/gallium/drivers/lima/ir/gp/lower.c

@@ -323,7 +323,7 @@ static bool gpir_lower_eq_ne(gpir_block *block, gpir_node *node)
          node_new_op = gpir_op_max; /* or */
          break;
       default:
-         assert(0);
+         unreachable("bad node op");
    }
 
    gpir_alu_node *e = gpir_node_to_alu(node);

src/gallium/drivers/lima/ir/pp/nir.c

@@ -305,7 +305,7 @@ static bool ppir_emit_intrinsic(ppir_block *block, nir_instr *ni)
          op = ppir_op_load_frontface;
          break;
       default:
-         assert(0);
+         unreachable("bad intrinsic");
          break;
       }