refactor(build): reorder platform Makefile evaluation

Commit(f5211420b refactor(cpufeat): refactor arch feature build
options) ensures mandatory arch features are enabled based on
ARM_ARCH_MAJOR and ARM_ARCH_MINOR, which would be expected to be
provided from platform makefile. However it missed ensuring platform
makefile is included before parsing and enabling any mandatory arch
features.

Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
Change-Id: Ia0ccb7d73b2d24c87d3d235babed4704230bec28
2 files changed