linux: Build $KERNEL_UBOOT_EXTRA_TARGET before kernel image

When there is a need to build the kernel with appended device tree for compatibility with older bootloaders,
$KERNEL_UBOOT_EXTRA_TARGET, which usually is a list of device tree source files, needs to be built
before the kernel, making device tree binaries available for appending to the kernel image.
kodi: add PR5963

Signed-off-by: Stephan Raue <stephan@openelec.tv>
kodi: move imx6 powermenu patch to project dir

Signed-off-by: Stephan Raue <stephan@openelec.tv>
projects/RPi/patches/kodi: update RPi support patch

Signed-off-by: Stephan Raue <stephan@openelec.tv>
bcm2835-driver: update to bcm2835-driver-833534c

Signed-off-by: Stephan Raue <stephan@openelec.tv>
bcm2835-bootloader: update to bcm2835-bootloader-833534c

Signed-off-by: Stephan Raue <stephan@openelec.tv>
kodi: update to kodi-14-6cbc3ef

Signed-off-by: Stephan Raue <stephan@openelec.tv>
Merge pull request #3701 from codesnake/kernel_with_appended_dtb

linux: Build $KERNEL_UBOOT_EXTRA_TARGET before kernel image