SMCCC/PCI: Handle std svc boilerplate

Add SMC wrappers for handshaking the existence
and basic parameter validation for the SMCCC/PCI
API. The actual read/write/segment validation is
implemented by a given platform which will enable
the API by defining SMC_PCI_SUPPORT.

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Change-Id: I4485ad0fe6003cec6f5eedef688914d100513c21
3 files changed