All platform specific configuration is moved out into separate files so
that the main makefile only contains common code. Choose which files to
include based on the values of u-boot configuration variables. Currently
these four U-Boot variables are used:
   CONFIG_SYS_VENDOR ==> include scripts/vendor-$(CONFIG_SYS_VENDOR).mk
   CONFIG_SYS_SOC ==> include scripts/soc-$(CONFIG_SYS_SOC).mk
   CONFIG_SYS_BOARD ==> include scripts/board-$(CONFIG_SYS_BOARD).mk
   CONFIG_SYS_CONFIG_NAME ==> include scripts/config-$(CONFIG_SYS_CONFIG_NAME).mk

Signed-off-by: Grant Likely <grant.likely@arm.com>