uboot-imx

Fix "ld: cannot find -lstubs" build error

Commit 1bc15386 moved the examples/ to examples/standalone but failed
to adapt the Makefiles that need to link against libstubs.a

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Signed-off-by: Peter Tyser <ptyser@xes-inc.com>