uboot-imx

imx-common: compile plugin code

If CONFIG_USE_IMXIMG_PLUGIN is selected, plugin.bin will be
generated under board/$(BOARDDIR)/.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Reviewed-by: Tom Rini <trini@konsulko.com>