arch-arm: python3 "/" will always produce a float

arch-arm: python3 "/" will always produce a float

"/" was ambiguous in python2 and was producing a floor (integer)
division if the operands were int or long.
In python3 "/" will always produce a float which makes it unsuitable
in cases where an integer is expected

PEP238: https://www.python.org/dev/peps/pep-0238/

Change-Id: I481cf1e9c0f95a6f47ecf6539eee0c9bcaf31e17
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/26247
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>