There are still some missing parts (e.g. board support, device trees),
but with these bits added on top of this patch I can successfully boot a
EFM32GG-DK3750 board that uses an EFM32GG990F1024.
# Empty file waiting for deletion once Makefile.boot isn't needed any more.
# Patch waits for application at
# http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=7889/1 .