groff: Fix determinism issue

Sometimes bison would regenerate source files and sometimes it would not
This is likely related to the patching of generated files by on of the
patches.

Drop those changes and force the files to regenerate in all cases since
we depend on bison-native anyway. This ensures the results are always
consistent.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>