ramips: mt76x8: fix build due to renamed U-Boot binary

The U-Boot binary for the RAVPower RP-WD009 has been renamed.
In order to be uniform with all other U-Boot binaries generated the SoC type has been prepended.
Set that new name also in the image build recipe for that device in order to fix build.

Fixes: 927334a8f7 ("uboot-mediatek: add basic build for ZBT-WG3526 (MT7621, 16M SPI-NOR)")
Signed-off-by: Daniel Golle <[email protected]>

target/linux/ramips/image/mt76x8.mk

@@ -493,7 +493,7 @@ define Device/ravpower_rp-wd009
   IMAGE_SIZE := 14272k
   DEVICE_VENDOR := RAVPower
   DEVICE_MODEL := RP-WD009
-  UBOOT_PATH := $(STAGING_DIR_IMAGE)/ravpower_rp-wd009-u-boot.bin
+  UBOOT_PATH := $(STAGING_DIR_IMAGE)/mt7628_ravpower_rp-wd009-u-boot.bin
   DEVICE_PACKAGES := kmod-mt76x0e kmod-usb2 kmod-usb-ohci \
 	kmod-sdhci-mt7620 kmod-i2c-mt7628 ravpower-mcu
   IMAGES += factory.bin