r/z/zephyr-kernel-src-2.6.0.inc: Update ref of zephyrproject-rtos/trusted-firmware-m

It looks like legacy branch has been cleaned from upstream, only master remains

https://github.com/zephyrproject-rtos/trusted-firmware-m/branches

I used the revision on earlier version assuming it's closer to what we used before.

Also for the record USB console is working as documented at:

https://docs.oniroproject.org/projects/blueprints/en/latest/transparent-gateway.html

which is not the case in kirkstone branch
I'll diff to narrow the problem.

Relate-to: eclipse/oniro-core/meta-zephyr-bsp#1
Relate-to: eclipse-wg/oniro-wg/proposal-incubation-stage-oniro/proposal-incubation-oniro-marketing#43
Forwarded: eclipse/oniro-core/meta-zephyr-bsp!2


Signed-off-by: Philippe Coval <philippe.coval.ext@huawei.com>