linux-raspberrypi: add UBOOT_ENTRYPOINT to match LOADADDR
linux-raspberrypi: add UBOOT_ENTRYPOINT to match LOADADDR

This is so that uboot fit images have an entry point that matches the
LOADADDR that everything is expecting.

Signed-off-by: AJ Bagwell <e4f35219ff94e462f14cc4f20d8df19f74440407@hivehome.com>

agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,agherzan/meta-raspberrypi