firmware: arm_ffa: Add support for handling framework notifications

firmware: arm_ffa: Add support for handling framework notifications

Currently FF-A specification defines only one framework notification:
RX buffer full notification. This notification is signaled by the
partition manager during transmission of a partition message through
indirect messaging to,

1. Notify an endpoint that it has a pending message in its Rx buffer.
2. Inform the message receiver’s scheduler via the schedule receiver
   interrupt that the receiver must be run.

In response to an FFA_MSG_SEND2 invocation by a sender endpoint, the
framework performs the following actions after the message is copied
from the Tx buffer of the sender to the Rx buffer of the receiver:

1. The notification is pended in the framework notification bitmap of
   the receiver.
2. The partition manager of the endpoint that contains receiver’s
   scheduler pends the schedule receiver interrupt for this endpoint.

The receiver receives the notification and copies out the message from
its Rx buffer.

Tested-by: Viresh Kumar <viresh.kumar@linaro.org>
Message-Id: <20250217-ffa_updates-v3-17-bd1d9de615e7@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>