kbuild: Drop support for clean-rule

clean-rule has not been used since 94869f86 (kbuild: Accept absolute
paths in clean-files and introduce clean-dirs) ten years ago.

Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
1 file changed