kirkwood: support sysupgrade on Linksys EA[34]500

This automatically writes to the alternate firmware partition
(on Linksys's dual firmware layout) using code borrowed from
the WRT1900AC port.

Signed-off-by: Claudio Leite <leitec@staticky.com>

SVN-Revision: 47434

target/linux/kirkwood/base-files/lib/upgrade/platform.sh

@@ -0,0 +1,32 @@
+. /lib/kirkwood.sh
+
+platform_check_image() {
+	[ "$#" -gt 1 ] && return 1
+	local board="$(kirkwood_board_name)"
+	local magic="$(get_magic_long "$1")"
+
+	case "$board" in
+	"linksys-audi"|\
+	"linksys-viper")
+		[ "$magic" != "27051956" -a "$magic" != "73797375" ] && {
+			echo "Invalid image type."
+			return 1
+		}
+		return 0
+		;;
+	esac
+
+	echo "Sysupgrade is not yet supported on $board."
+	return 1
+}
+
+platform_do_upgrade() {
+	local board="$(kirkwood_board_name)"
+
+	case "$board" in
+	"linksys-audi"|\
+	"linksys-viper")
+		platform_do_upgrade_linksys "$ARGV"
+		;;
+	esac
+}