umh: Rename the user mode driver helpers for clarity

Now that the functionality of umh_setup_pipe and
umh_clean_and_save_pid has changed their names are too specific and
don't make much sense.  Instead name them  umd_setup and umd_cleanup
for the functional role in setting up user mode drivers.

v1: https://lkml.kernel.org/r/875zbegf82.fsf_-_@x220.int.ebiederm.org
v2: https://lkml.kernel.org/r/87tuyt63x3.fsf_-_@x220.int.ebiederm.org
Link: https://lkml.kernel.org/r/20200702164140.4468-3-ebiederm@xmission.com


Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>