MIPS: VR41xx: Drop redundant spinlock initialization

slot_errbuf_lock has declared and initialized by DEFINE_SPINLOCK,
so we don't need to spin_lock_init again, drop it.

Signed-off-by: Haowen Bai <baihaowen@meizu.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>