feat(spmc): add support for FF-A power mgmt. messages in the EL3 SPMC

This patch adds support for forwarding the following PSCI messages
received by the SPMC at EL3 to the S-EL1 SP if the SP has indicated
that it wishes to receive the appropriate message via its manifest.

1. A PSCI CPU_OFF message in response to a cpu hot unplug request
   from the OS.
2. A message to indicate warm boot of a cpu in response to a cpu
   hot plug request from the OS.
3. A PSCI CPU_SUSPEND message in response to a cpu idle event
   initiated from the OS.
4. A message to indicate warm boot of a cpu from a shallow power
   state in response to a cpu resume power event.

This patch also implements the FFA_SECONDARY_EP_REGISTER function to
enable the SP specify its secondary entrypoint.

Signed-off-by: Achin Gupta <achin.gupta@arm.com>
Signed-off-by: Marc Bonnici <marc.bonnici@arm.com>
Change-Id: I375d0655b2c6fc27445facc39213d1d0678557f4
9 files changed