Documentation: Document the RB532 specific kmac tag

The Routerboard 532 bootloader passes the korina ethernet
MAC adapter address to the kernel on the command line.
Document this in the kernel-parameters file.

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 329dcab..d0fff63 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1014,6 +1014,10 @@
 			(only serial suported for now)
 			Format: <serial_device>[,baud]
 
+	kmac=		[MIPS] korina ethernet MAC address.
+			Configure the RouterBoard 532 series on-chip
+			Ethernet adapter MAC address.
+
 	l2cr=		[PPC]
 
 	l3cr=		[PPC]