panfrost: gen_pack: Minor formatting improvement

Escape the \ in pan_pack() so the end result is actually a multi-line
macro.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6797>
1 file changed