run_config: use payload UART as primary UART

Open-CI cannot use primary and payload UARTs at the same time, so
payload UART was used as primary UART.
Additionally, this change required the creation of tftf-non-primary.exp
for lava.

Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
Change-Id: I70d08972f6f5e69ba70575fa6c6ed6895471d42e
2 files changed