dev-arm: Use getIntConfig when reading/writing GICD_ICFGR

dev-arm: Use getIntConfig when reading/writing GICD_ICFGR

This patch is changing the getIntConfig helper (which has been
used so far by isLevelSensitive only) to make it usable by the
read/writes of the GICD_ICFGR register.

While the helper was previously returning the irq config bits
provided a single irq as an input, this new version is returning
the entire GICD_ICFGR word (read/writable)

JIRA: https://gem5.atlassian.net/browse/GEM5-667

Change-Id: I07e455a9e2819fed1f97a0e372d9d9a2e5ad4801
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/31055
Reviewed-by: Hsuan Hsu <kugwa2000@gmail.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>