platforms/rddaniel: update rnsam location flag name

The model flag FASTSIM_CMN600_INTERNAL_RNSAM has been renamed as
FASTSIM_CMN_INTERNAL_RNSAM. Update the run model script
accordingly.

Change-Id: I5f8dd22e4e7d097c84b1c7ff9575d616d2ecbafc
Signed-off-by: Thomas Abraham <thomas.abraham@arm.com>