mem-ruby: fix MI_example functional read

Changing AccessPermission to Read_Write for transient states waiting
on memory when to or from Invalid. In all cases the memory will have
the latest data, so this also modifies functionalRead to always send
the access to memory.

Change-Id: I99f557539b4f9d0d2f99558752b7ddb7e85ab3c6
Signed-off-by: Tiago Mück <tiago.muck@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/41853
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
1 file changed