Make flash area size configurable

UEFI tests require more space for the authenticated variable tests
so the flash size is changed to be configurable. On FVP it will have
an increased size.

Signed-off-by: Gabor Toth <gabor.toth2@arm.com>
Change-Id: Ifac6b98cdb241474fd3f61411a546efd540496fb
7 files changed