cpu: Add byteEnable assertions to readMem and initateMemRead

cpu: Add byteEnable assertions to readMem and initateMemRead

Those are already present in writeMem; looking for consistency

Change-Id: Ib85e0db228bc73e3ac64155d1290444cf6864a8c
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/23281
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>