MAINTAINERS: rename cifs_common to smbfs_common in cifs and ksmbd entry

commit 23e91d8b

("cifs: rename cifs_common to smbfs_common") cause
the following warning from get_maintainer.pl.

./scripts/get_maintainer.pl --self-test=patterns complains:
  warning: no file matches    F:    fs/cifs_common/

This patch rename cifs_common to smbfs_common in cifs and ksmbd entry.

Reported-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>