Add preliminary support for sysupgrade on brcm

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@8718 3c298f89-4303-0410-b956-a3cf2f4a3e73

target/linux/brcm-2.4/base-files/default/lib/upgrade/platform.sh

@@ -0,0 +1,24 @@
+platform_check_image() {
+	[ "$ARGC" -gt 1 ] && return 1
+
+	case "$(get_magic_word "$1")" in
+		# .trx files
+		4844) return 0;;
+		# .bin files
+		5735) return 0;;
+		*)
+			echo "Invalid image type"
+			return 1
+		;;
+	esac
+}
+
+platform_do_upgrade() {
+	get_image "$1" > $(find_mtd_part "linux")
+	sync
+}
+
+brcm_prepare_mtd() {
+	[ "$SAVE_CONFIG" -eq 1 ] && return 0
+}
+append sysupgrade_pre_upgrade brcm_prepare_mtd