As with previous patches, unify those 2 functions into a single function
v9fs_tmkdir() by using a declarative function arguments approach.

Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Message-Id: <b87b2c972921df980440ff5b2d3e6bb8163d6551.1664917004.git.qemu_oss@crudebyte.com>