When accessing memory using functionalAccess(), the MMU could tell us to
use a nonsecure access even though the CPU is operating in secure mode.
I noticed this while trying to run a simple semihosting hello world with
the MMU+caches enabled and the semihosting calls ended up reading from
memory instead of the caches due to an S/NS mismatch.
See also https://github.com/gem5/gem5/pull/1198 which happens to also
mask the issue I saw, but I believe both changes are needed.
Change-Id: I9e6b9839b194fbd41938e2225449c74701ea7fee
3cfc550fc0