libsp: Introduce FF-A support.

libsp is intended to provide a common set of features for SEL-0 secure
partitions. This includes the FF-A ABI and higher level functions. In
this commit the minimal set of FF-A calls is implemented to provide
compliance.

Signed-off-by: Imre Kis <imre.kis@arm.com>
Change-Id: I5420a11a7dc75b228d0d0d58059dea86e5f927ee
11 files changed