At present, the build option checks are done prior to inclusion of
BL makefiles. This meant if the BL makefiles modified any of the options
then these checks were bypassed. This patch corrects this problem.

Change-Id: I0b591392a74d6d456d2b19bbe292f42b5aeae048
Signed-off-by: Soby Mathew <soby.mathew@arm.com>