ARM TF-A reports compatibility with PSCI v1.1 since v1.5. Upstream
ARM TF-A support for STM32MP was introduced with v1.6.
It's thus safe to assume that the STM32MP barebox will never have to
interact with a secure monitor implementing PSCI v0.1.

Overwrite the psci device tree compatible to specify v0.2. This is the
first version that implements PSCI_VERSION, which allows the barebox
psci client driver selected in this commit to query the actual PSCI
version and fix it up into the device tree.

This fixes an issue where resetting via PSCI fails in Linux because the
upstream device tree compatible:

  reboot: Restarting system
  Reboot failed -- System halted

Reported-by: Michael Olbrich <mol@pengutronix.de>
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>