rom_chain_image() function

Chain into a launchable image Searches a memory region for a launchable image, and executes it if possible. The region_base and region_size specify a word-aligned, word-multiple-sized area of RAM, XIP RAM or flash to search. The first 4 kiB of the region must contain the start of a Block Loop with an IMAGE_DEF. If the new image is launched, the call does not return otherwise an error is returned. The region_base is signed, as a negative value can be passed, which indicates that the (negated back to positive value) is both the region_base and the base of the "flash update" region. This method potentially requires similar complexity to the boot path in terms of picking amongst versions, checking signatures etc. As a result it requires a user provided memory buffer as a work area. The work area should be word aligned, and of sufficient size or BOOTROM_ERROR_INSUFFICIENT_RESOURCES will be returned. The work area size currently required is 3064, so 3K is a good choice. NOTE: This method is primarily expected to be used when implementing bootloaders. NOTE: When chaining into an image, the OTP_DATA_BOOT_FLAGS0_ROLLBACK_REQUIRED flag will not be set, to prevent invalidating a bootloader without a rollback version by booting a binary which has one.