firmware: arm_ffa: Avoid queuing work when running on the worker queue

firmware: arm_ffa: Avoid queuing work when running on the worker queue

Currently notif_pcpu_irq_work_fn() may get queued from the work that is
already running on the 'notif_pcpu_wq' workqueue. This may add
unnecessary delays and could be avoided if the work is called directly
instead.

This change removes queuing of the work when already running on the
'notif_pcpu_wq' workqueue thereby removing any possible delays in that
path.

Link: https://lore.kernel.org/r/20240424131640.706870-1-sudeep.holla@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>