configs/stm32mp157c_dk2_defconfig: update arm-trusted-firmware to lts-v2.8.13

The assumption is that updates to the stable branch should not break anything,
so we use the latest LTS rather than a specific version.

Signed-off-by: Marleen Vos <marleen.vos@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
1 file changed