Note that the arguments passed during the SMC call don't comply with the
SPCI specifications. This will be fixed in following patches, but it is
needed to implement a few more SPCI SMCs to be able to do it. The
current code allows us to start testing it.

Change-Id: Ic13dcc54c40327df03be1b0f52e8a44f468f06b4
Co-authored-by: Jean-Paul Etienne <jean-paul.etienne@arm.com>
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>