Blackfin: link with normal ABI target

If someone uses the FDPIC toolchain to compile U-Boot, make sure the
linker knows to use the normal ABI target rather than the FDPIC one.
This wasn't needed with older toolchains, but when we fixed the linker
such that the default target changed based on tuple, this broke.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>