dt-bindings: clock: Fix documentation for Xilinx ZynqMP clock driver

dt-bindings: clock: Fix documentation for Xilinx ZynqMP clock driver

Documentation is fixed to reflect recent changes in clock tree:
- Clock ID definitions have changed for gem-related clock IDs
- New clock IDs are defined to distinguish external (E)MIO sources
  for gem Tx and Rx clocks
- New clock ID is defined for acpu full clock

Signed-off-by: Mirela Simonovic <mirela.simonovic@aggios.com>
Acked-by: Will Wong <willw@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>