iscsi_ibft: Add prefix-len attr and display netmask

The iBFT table only specifies a prefix length, not a netmask.
And the netmask is pretty much pointless for IPv6.
So introduce a new attribute 'prefix-len'.

Some older user-space code might rely on the netmask attribute
being present, so we should always display it.

Changes from v1:
 - Combined two patches into one

Changes from v2:
 - Cleaned up/corrected wording for patch description

v3: [Put Hannes back as author]

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Lee Duncan <lduncan@suse.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Konrad Rzeszutek Wilk <konrad@kernel.org>
diff --git a/drivers/firmware/iscsi_ibft.c b/drivers/firmware/iscsi_ibft.c
index 7279123..81037e5 100644
--- a/drivers/firmware/iscsi_ibft.c
+++ b/drivers/firmware/iscsi_ibft.c
@@ -319,6 +319,9 @@
 		val = cpu_to_be32(~((1 << (32-nic->subnet_mask_prefix))-1));
 		str += sprintf(str, "%pI4", &val);
 		break;
+	case ISCSI_BOOT_ETH_PREFIX_LEN:
+		str += sprintf(str, "%d\n", nic->subnet_mask_prefix);
+		break;
 	case ISCSI_BOOT_ETH_ORIGIN:
 		str += sprintf(str, "%d\n", nic->origin);
 		break;
@@ -460,6 +463,7 @@
 		if (address_not_null(nic->ip_addr))
 			rc = S_IRUGO;
 		break;
+	case ISCSI_BOOT_ETH_PREFIX_LEN:
 	case ISCSI_BOOT_ETH_SUBNET_MASK:
 		if (nic->subnet_mask_prefix)
 			rc = S_IRUGO;