powerpc/powernv: Rate limit opal-elog read failure message

Sometimes we can't read an error log from OPAL, and we print an error
message accordingly. But the OPAL userspace tools seem to like retrying a
lot, in which case we flood the kernel log with a lot of messages.

Change pr_err() to pr_err_ratelimited() to help with this.

Signed-off-by: Andrew Donnellan <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/powerpc/platforms/powernv/opal-elog.c

···
 		opal_rc = opal_read_elog(__pa(elog->buffer),
 					 elog->size, elog->id);
 		if (opal_rc != OPAL_SUCCESS) {
-			pr_err("ELOG: log read failed for log-id=%llx\n",
-			       elog->id);
+			pr_err_ratelimited("ELOG: log read failed for log-id=%llx\n",
+					   elog->id);
 			kfree(elog->buffer);
 			elog->buffer = NULL;
 			return -EIO;