sparc: serial: sunhv: fix a double lock bug

We accidentally take the "port->lock" twice in a row.  This old code
was supposed to be deleted.

Fixes: e58e241c ('sparc: serial: Clean up the locking for -rt')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>