brcm63xx: fix invalid Asmax AR 1004g DTS reference

Build profile for Asmax AR 1004g refers to an invalid DTS "rg100a". The
correct DTS for this device is "ar1004g".

Signed-off-by: Marcin Jurkowski <marcin1j@gmail.com>

target/linux/brcm63xx/image/bcm63xx.mk

@@ -229,7 +229,7 @@ TARGET_DEVICES += RG100A
 define Device/AR1004G
   $(Device/bcm63xx)
   DEVICE_TITLE := Asmax AR 1004g
-  DEVICE_DTS := rg100a
+  DEVICE_DTS := ar1004g
   CFE_BOARD_ID := 96348GW-10
   CFE_CHIP_ID := 6348
   DEVICE_PACKAGES := \