dt-bindings: PCI: microchip,pcie-host: Fix DMA coherency property

PolarFire SoC may be configured in a way that requires non-coherent DMA
handling. On RISC-V, buses are coherent by default & the dma-noncoherent
property is required to denote buses or devices that are non-coherent.
For some reason, instead of adding dma-noncoherent to the binding
the pointless, NOP, property dma-coherent was. Swap dma-coherent for
dma-noncoherent.

Fixes: 04aa999e ("dt-bindings: PCI: microchip,pcie-host: Allow dma-noncoherent")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Link: https://lore.kernel.org/r/20250516-datebook-senator-ff7a1c30cbd5@spud