docs: add stub header for u_format_gen.h

Warning, treated as error:
docs/isl/aux-surf-comp.rst:51:docs/../src/util/format/u_formats.h:33: 'util/format/u_format_gen.h' file not found

Fixes: e05415a82e ("format: Generate endian-independent format aliases")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30339>
This commit is contained in:
Eric Engestrom 2024-07-24 11:26:09 +02:00
parent c30e5d44b1
commit e634acaf88