mvebu: Add subtarget for Cortex A9 build

This is in preparation for adding a subtarget for the Cortex A53 later.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

target/linux/mvebu/cortexa9/target.mk

@@ -0,0 +1,14 @@
+#
+# Copyright (C) 2017 Hauke Mehrtens
+#
+# This is free software, licensed under the GNU General Public License v2.
+# See /LICENSE for more information.
+#
+
+include $(TOPDIR)/rules.mk
+
+ARCH:=arm
+BOARDNAME:=Marvell Armada 37x/38x/XP
+CPU_TYPE:=cortex-a9
+CPU_SUBTYPE:=vfpv3
+KERNELNAME:=zImage dtbs