firmware: arm_ffa: Handle ffa_notification_get correctly at virtual FF-A instance

Currently it is assumed that the driver always calls ffa_notification_get()
at the NS physical FF-A instance to request the SPMC to return pending
SP or SPM Framework notifications. However, in order to support the driver
invoking ffa_notification_get() at virtual FF-A instance, we need to make
sure correct bits are enabled in the bitmaps enable flag.

It is expected to have hypervisor framework and VM notifications bitmap
to be zero at the non-secure physical FF-A instance.

Message-Id: <20250217-ffa_updates-v3-19-bd1d9de615e7@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>