checkpatch: mark kunmap() and kunmap_atomic() deprecated

checkpatch: mark kunmap() and kunmap_atomic() deprecated

It was suggested by Fabio that kunmap() be marked deprecated in
checkpatch.[1] This did not seem necessary until an invalid conversion of
kmap_local_page() appeared in mainline.[2][3] The introduction of this bug
would have been flagged with kunmap() being marked deprecated.

Add kunmap() and kunmap_atomic() to checkpatch to help prevent further
confusion.

[1] https://lore.kernel.org/all/1884934.6tgchFWduM@suse/
[2] d406d26745ab ("cifs: skip alloc when request has no pages")
[3] https://lore.kernel.org/r/20221229-cifs-kmap-v1-1-c70d0e9a53eb@intel.com

Link: https://lkml.kernel.org/r/20221229-kmap-checkpatch-v2-1-919fc4d4e3c2@intel.com
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Suggested-by: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
Acked-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>