This allows secure partitions to access these registers. This is
needed in some cases. For example, it has been reported that in order
to implement secure storage services, a secure partition needs to
encrypt/decrypt some authentication variables, which requires FP/SIMD
support.

Note that SPM will not do any saving/restoring of these registers on
behalf of the SP. This falls under the SP's responsibility.

Also note that if the SP gets preempted, it might not get a chance to
save/restore FP/SIMD registers first. This patch does not address this
problem. It only serves as a temporary solution to unblock development
on the secure partition side.

Change-Id: I3b8ccdebdac0219f6ac96ad66ab2be0be8374ad3
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>