firmware: arm_ffa: Fix ffa_notification_info_get() IDs handling

firmware: arm_ffa: Fix ffa_notification_info_get() IDs handling

To parse the retrieved ID lists appropriately in
ffa_notification_info_get() the ids_processed variable should not
be pre-incremented - we are dropping an identifier at the
beginning of the list.

Fix it by using the post-increment operator to increment the number
of processed IDs.

Fixes: 3522be48d82b ("firmware: arm_ffa: Implement the NOTIFICATION_INFO_GET interface")
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lore.kernel.org/r/20231108111549.155974-1-lpieralisi@kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>