tty: serial: linflexuart: Use DEFINE_SPINLOCK() for spinlock

spinlock can be initialized automatically with DEFINE_SPINLOCK()
rather than explicitly calling spin_lock_init().

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20190827114614.102037-1-weiyongjun1@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>