arch-arm: Interface for the ArmStaticInst intWidth field

arch-arm: Interface for the ArmStaticInst intWidth field

ARMv8 Tracers might want to be able to read the intWidth field of the
ArmStaticInst object. The field is specifying the bit width of the
integer registers used by the current instruction.

Change-Id: Iaee3123823a2c7380917001c453377c1c12e54a7
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/5661
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>