mkimg: don't copy boot firmware

* Raspberry Pi 5 firmware is self-contained in the bootloader EEPROM:
  https://www.raspberrypi.com/documentation/computers/config_txt.html#start_file-fixup_file

mkbootimg.mk

@@ -6,7 +6,6 @@
 
 DEVICE_PATH := device/brcm/rpi5
 KERNEL_PATH := device/brcm/rpi5-kernel
-VENDOR_PATH := vendor/brcm
 
 RPI_BOOT_OUT := $(PRODUCT_OUT)/rpiboot
 $(RPI_BOOT_OUT): $(INSTALLED_RAMDISK_TARGET)
@@ -17,7 +16,6 @@ $(RPI_BOOT_OUT): $(INSTALLED_RAMDISK_TARGET)
 	cp $(KERNEL_PATH)/bcm2712-rpi-*.dtb $(RPI_BOOT_OUT)
 	cp $(KERNEL_PATH)/overlays/* $(RPI_BOOT_OUT)/overlays
 	cp $(PRODUCT_OUT)/ramdisk.img $(RPI_BOOT_OUT)
-	cp $(VENDOR_PATH)/rpi5/proprietary/boot/* $(RPI_BOOT_OUT)
 	echo $(BOARD_KERNEL_CMDLINE) > $(RPI_BOOT_OUT)/cmdline.txt
 
 $(INSTALLED_BOOTIMAGE_TARGET): $(RPI_BOOT_OUT)