Hi,
We just added TARGET_CPU_VARIANT:= generic in device /linaro/iMX53/BoardConfig.mk file.
Then we got error saying no uboot diectory, as of now uboot was not required as we already have uboot image for imx53.
So commented below line in "device/linaro/common/tasks/kernel.mk" file
#BOOTLOADER_DEP := $(PRODUCT_OUT)/u-boot.bin