llvmpipe: Drop switch with only default case

Replace it with the default case contents.

Avoids clang warning about the fall-through annotation.

Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10220>

src/gallium/drivers/llvmpipe/lp_screen.c

@@ -377,11 +377,8 @@ llvmpipe_get_shader_param(struct pipe_screen *screen,
          else
             return PIPE_SHADER_IR_NIR;
       }
-      switch (param) {
-      default:
-         return gallivm_get_shader_param(param);
-      }
-      FALLTHROUGH;
+
+      return gallivm_get_shader_param(param);
    case PIPE_SHADER_TESS_CTRL:
    case PIPE_SHADER_TESS_EVAL:
       /* Tessellation shader needs llvm coroutines support */