arch-arm: raise/clear IRQ when writing to PMOVSCLR/SET

arch-arm: raise/clear IRQ when writing to PMOVSCLR/SET

Writing a 1 to the Overflow Flag Status register should trigger an
interrupt raise/clear depending on the register we are currently using
(PMOVSCLR for clearing and PMOVSSET for raising).

Change-Id: I2091456685a245712045cf7a4932ac36b7dded1d
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/12531
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>