Create a relocatable instance of ubldr for ARM. The original ubldr,
static-linked to run at a fixed position, is still installed to maintain
compatibility with existing configurations. The makefile now also creates
and installs ubldr.bin, a stripped binary (no elf headers) with an entry
point offset of 0 that can be loaded by u-boot at any address and launched
with "go ${loadaddr}".

To use ubldr.bin, U-Boot must still be built with the CONFIG_API option,
but no longer needs the CONFIG_ELF option.