Fix checker to work in newmem in SE mode.

Fix checker to work in newmem in SE mode.

src/cpu/o3/fetch_impl.hh:
    Give the checker a pointer to the icachePort.
src/cpu/o3/lsq_unit_impl.hh:
    Give the checker a pointer to the dcachePort.
src/mem/request.hh:
    Allow checking for the scResult being valid prior to accessing it.

--HG--
extra : convert_revision : ced4180588d242111ecba4a11586823badd6cf15