riscv: dts: sync mpfs-icicle devicetree with linux

The "notable" disappearances are:
- the pac193x stanza - there's nothing in mainline linux w.r.t. bindings
  for this & what is going to appear in mainline linux is going to be
  incompatible with what is currently in U-Boot.
- operating points - these operating points should not be set at the
  soc.dtsi level as they may not be possible depending on the design
  programmed to the FPGA
- clock output names - there are defines for the clock indices, these
  should not be needed
- the dt maintainers in linux NAKed using defines for IRQ numbers
- the qspi nand, which is not part of the icicle's default configuration
  is removed.

Reviewed-by: Padmarao Begari <padmarao.begari@microchip.com>
Tested-by: Padmarao Begari <padmarao.begari@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Rick Chen <rick@andestech.com>