vmw_balloon: release lock on error in vmballoon_reset()

We added some locking to this function but forgot to drop the lock on
these two error paths.  This bug would lead to an immediate deadlock.

Fixes: c7b3690f

 ("vmw_balloon: stats rework")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable@vger.kernel.org
Reviewed-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>