- Enable ums (USB Mass Storage) support that allows to mount onboard
  mass storage devices like eMMC and SD card on external host machine.
  This can be a convenient method to install software on onboard devices.
- Remove configuration settings duplicated (and outdated) in pitx-imx8.h
  config file.

Signed-off-by: Thomas Schaefer <thomas.schaefer@kontron.com>