bootscript[-alt|-uboot]: place boot.cfg and variants into deploy directory

boot.cfg and similar files are installed into /boot folder of rootfs. For the rauc bootfs-image and the WIC image they are also needed in the deploy folder and the IMAGE_BOOT_FILES variable. As the selection of the specific bootfiles is already done using the packages, the IMAGE_BOOT_FILES variable is configured to install everything from the boot/ subdir in the deploy path and the packages deploy the needed scripts there.

Signed-off-by: Mikhail Vanyulin mikhail.vanyulin@rtsoft.de