yocto/trusted-firmware-m-scripts: Use same SHA as TF-M

The TF-M rd-n2-automotive BSP is based on a SHA on the development
branch. Use the same SHA for the scripts that are used to sign the RSS
images.

Issue-Id: SCM-5314
Signed-off-by: Peter Hoyes <Peter.Hoyes@arm.com>
Change-Id: I08738cd28d391d75a362a0737becfea29ebb0792