pan/decode: Fix tiler warning

pan/decode: Fix tiler warning

../src/panfrost/pandecode/decode.c:1176:60: warning: taking address of
packed member of ‘struct mali_framebuffer’ may result in an unaligned
pointer value [-Waddress-of-packed-member]
 1176 |
      pandecode_midgard_tiler_descriptor(&fb->tiler, fb->width1 + 1,
fb->height1 + 1, is_fragment, true);

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5219>