firmware: arm_ffa: Replace UUID buffer to standard UUID format

Currently ffa_partition_info structure holds the UUID in the format
compatible with the firmware interface. However, most of the functions
in the FF-A core driver deals directly with uuid_t type.

Replace UUID buffer to standard UUID format in the ffa_partition_info
structure.

Tested-by: Viresh Kumar <viresh.kumar@linaro.org>
Message-Id: <20250217-ffa_updates-v3-2-bd1d9de615e7@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>