rdn1edge/run_model: align to changes in SCP/MCP firmware names

The SCP firmware binary names are now changed to *cp_romfw.bin and
*cp_ramfw.bin. Align to these changes in the run_model script.

Change-Id: I077a83662b013f5764456c49cff30c36f8db86c5
Signed-off-by: Thomas Abraham <thomas.abraham@arm.com>