image: fit: Apply overlays using aligned writable FDT copies

image: fit: Apply overlays using aligned writable FDT copies

libfdt expects FDT/DTO blobs to be 8-byte aligned. When loading the
base FDT or overlays from a FIT, the mapped buffer may be unaligned,
which can break fdt_open_into() on strict-alignment architectures.

boot_get_fdt_fit() relocates the base FDT with boot_relocate_fdt()
before applying overlays. That uses the bootm memory map and can
overlap with the FIT buffer when the FIT is loaded into RAM,
corrupting data needed to load the kernel and ramdisk.

Allocate writable, 8-byte aligned copies of the base FDT and overlays
with memalign() and fdt_open_into(). Grow the base buffer as needed,
apply overlays to it and pack the final tree. Free each temporary
overlay copy after application and check fdt_pack() errors.

Fixes: 8fbcc0e0e839 ("boot: Assure FDT is always 8-byte aligned")
Fixes: 881f0b77dc8c ("image: apply FDTOs on FDT image node")
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Cc: Jamie Gibbons <Jamie.Gibbons@microchip.com>
Reviewed-by: Marek Vasut <marek.vasut@mailbox.org>