[PATCH] powerpc/powernv: check OPAL_REGISTER_DUMP_REGION calls exist

["Cédric Le Goater" <clg@fr.ibm.com>]

On Open Power systems, such call fails in OPAL : 

   OPAL: Called with bad token 101 !

The check on the OPAL_UNREGISTER_DUMP_REGION call is added for 
symmetry. I did not see any errors for it.

Signed-off-by: Cédric Le Goater <clg@fr.ibm.com>
---
 arch/powerpc/platforms/powernv/opal.c |    8 ++++++++
 1 file changed, 8 insertions(+)

Index: linux.git/arch/powerpc/platforms/powernv/opal.c
===================================================================
--- linux.git.orig/arch/powerpc/platforms/powernv/opal.c
+++ linux.git/arch/powerpc/platforms/powernv/opal.c
@@ -665,6 +665,11 @@ static void __init opal_dump_region_init
 	uint64_t size;
 	int rc;
 
+	if (!opal_check_token(OPAL_REGISTER_DUMP_REGION)) {
+		pr_warn("Firmware doesn't support dump region buffers\n");
+		return;
+	}
+
 	/* Register kernel log buffer */
 	addr = log_buf_addr_get();
 	size = log_buf_len_get();
@@ -794,6 +799,9 @@ void opal_shutdown(void)
 			mdelay(10);
 	}
 
+	if (!opal_check_token(OPAL_UNREGISTER_DUMP_REGION))
+		return;
+
 	/* Unregister memory dump region */
 	opal_unregister_dump_region(OPAL_DUMP_REGION_LOG_BUF);
 }