rdfremontcfg2/run_model: fix pcie param while passing sata disk image

Fix PCIe group param while passing the satadisk image as a preparation
to support distro boot for RD-Fremont-Cfg2

Reported-by: Nishant Sharma <nishant.sharma@arm.com>
Signed-off-by: Vijayenthiran Subramaniam <vijayenthiran.subramaniam@arm.com>
Change-Id: Ia7d65dc5abf9ae05ada87dd3602e556118dc03b0