ARM: rpc: check device_register return code in ecard_probe

device_register is marked __must_check, so we better propagate the error
value by returning it from ecard_probe.

Without this patch, building rpc_defconfig results in:

arch/arm/mach-rpc/ecard.c: In function 'ecard_probe':
arch/arm/mach-rpc/ecard.c:963:17: warning: ignoring return value of 'device_register', declared with attribute warn_unused_result [-Wunused-result]

Signed-off-by: Arnd Bergmann <[email protected]>
Cc: Russell King <[email protected]>
diff --git a/arch/arm/mach-rpc/ecard.c b/arch/arm/mach-rpc/ecard.c
index b91bc87..fcb1d59 100644
--- a/arch/arm/mach-rpc/ecard.c
+++ b/arch/arm/mach-rpc/ecard.c
@@ -960,7 +960,9 @@
 	*ecp = ec;
 	slot_to_expcard[slot] = ec;
 
-	device_register(&ec->dev);
+	rc = device_register(&ec->dev);
+	if (rc)
+		goto nodev;
 
 	return 0;