powerpc/pseries: Initialise nvram_pstore_info's buf_lock

nvram_pstore_info's buf_lock is not initialized before registering,
which is clearly incorrect.

It causes some strange behavior when trying to obtain the lock during
kdump process.

On a UP configuration, the console stopped for a couple of seconds, then
"lockup suspected" warning printed out, but then it continued to run.

So try lock fails, and lockup reported, but then arch_spin_lock()
passes.
Signed-off-by: NLi Zhong <zhong@linux.vnet.ibm.com>
[mpe: Edited changelog]
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/pseries/nvram.c

@@ -715,6 +715,8 @@ static int nvram_pstore_init(void)
 	nvram_pstore_info.buf = oops_data;
 	nvram_pstore_info.bufsize = oops_data_sz;
 
+	spin_lock_init(&nvram_pstore_info.buf_lock);
+
 	rc = pstore_register(&nvram_pstore_info);
 	if (rc != 0)
 		pr_err("nvram: pstore_register() failed, defaults to "