toradex: configblock: fix module revision in config block

U-boot might display wrong module revision information
for modules with an assembly version 'K'. "cfgblock create"
does not takes into account all revision digits from PID8.

This fix takes into account all digits of PID8
to store module revision.

Signed-off-by: Denys Drozdov <denys.drozdov@toradex.com>
Reviewed-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>