firmware: arm_ffa: Add support for passing UUID in FFA_MSG_SEND2

FF-A v1.2 introduces UUID field in partition message header used in
FFA_MSG_SEND2 to enable partitions/endpoints exposing multiple UUIDs.

Add the support for passing UUID in FFA_MSG_SEND2.

Tested-by: Viresh Kumar <viresh.kumar@linaro.org>
Message-Id: <20250217-ffa_updates-v3-10-bd1d9de615e7@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>