powerpc/eeh: Drop redundant spinlock initialization

[ Upstream commit 3def164a

 ]

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: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1652232476-9696-1-git-send-email-baihaowen@meizu.com
Stable-dep-of: 9aafbfa5

 ("powerpc/pseries/eeh: use correct API for error log size")
Signed-off-by: Sasha Levin <sashal@kernel.org>