Drivers: hv: utils: rename outmsg_lock

Drivers: hv: utils: rename outmsg_lock

As a preparation to reusing outmsg_lock to protect test-and-set openrations
on 'mode' rename it the more general 'lock'.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Orabug: 27426102
(cherry picked from commit a72f3a4ccff22de879a1f599210ecdd9bd483a43)
Signed-off-by: Jack Vogel <jack.vogel@oracle.com>
Reviewed-by: Tim Tianyang Chen <tianyang.chen@oracle.com>