ARM: dts: imx6ul: add more functionality to i.MX6UL

[Lothar Waßmann]

[PATCHv3 1/2] ARM: dts: imx6ul: add support for Ka-Ro electronics TXUL modules
[PATCHv3 2/2] ARM: dts: imx6ul: add support for Ka-Ro electronics TXUL mainboard

This patchset adds more functionality to the i.MX6UL machines.

Changes vs. v1:
- added patch to implement KPP clock for i.MX6UL to prevent conflicts
  when this patch would go via a different tree.
- added board support for Ka-Ro electronics TX6UL module for the same
  reason
- added imx6ul specific compatibles as requested by Lucas Stach

Changes vs. v2:
- dropped patches which have already been applied in the meantime
- addressed comments by Shawn Guo