rde1edge/run_model.sh: fix mcp uart out file

MCP firmware uses css uart in MCP address space rather than soc uart.
Fix the MCP's uart out file to use css uart.

Signed-off-by: Vijayenthiran Subramaniam <vijayenthiran.subramaniam@arm.com>
Change-Id: I592c1a0b40b86b62386149c22d71235469c6624f