arch-arm, cpu: fix ARM ubsan build on GCC 7.4.0

In src/cpu/reg_class.hh, numPinnedWrites was unset because the
constructors were not well factored out.

Change-Id: Ib2fc8d34a1adf5c48826d257a31dd24dfa64a08a
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20048
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
3 files changed