MIPS: Alchemy: Use DEFINE_SPINLOCK() for spinlock

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

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Lifu Chen <chenlifu@huawei.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>