optee: add per cpu asynchronous notification

Implements use of per-cpu irq for optee asynchronous notification.

Existing optee async notif implementation allows OP-TEE world to
raise an interrupt on which Linux optee driver will query some pending
events. This change allows the signaling interrupt to be a per-cpu
interrupt as with Arm GIC PPIs. Using a PPI instead of an SPI is useful
when no GIC lines are provisioned in the chip design and there are spare
PPI lines.

Cc: Jens Wiklander <jens.wiklander@linaro.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Marc Zyngier <maz@kernel.org>

Co-developed-by: Alexandre Torgue <alexandre.torgue@foss.st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
[JW: fixing a spell error in @notif_pcpu_wq description]
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>