arch-arm: IsStoreConditional flag set depending on flavor

arch-arm: IsStoreConditional flag set depending on flavor

This patch is aligning A32 with A64 where the IsStoreConditional flag
doesn't have to be specified manually in the instruction implementation,
but will be automatically added to any exclusive store.

Change-Id: Id02ed6fc2beeca6d125017393714a7c6eb3d8a33
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/15816
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>