uboot-imx

binman: Remove hard-coded file name for x86 CMC/FSP/VGA

Now that we have added file names from Kconfig in x86 u-boot.dtsi,
update binman to avoid using hard-coded names.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>