HID: hid-steam: Mutex cleanup in steam_set_lizard_mode()

Both branches of this if/else start with mutex_lock and end with mutex_unlock.
This hoists the mutex lock/unlock outside of the if statement for simplicity.

Signed-off-by: Vicki Pfau <vi@endrift.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>