dt-binding: spi: npcm-pspi: Add npcm845 compatible

Add a compatible string for Nuvoton BMC NPCM845 PSPI.
Signed-off-by: NTomer Maimon <tmaimon77@gmail.com>
Link: https://lore.kernel.org/r/20220722114136.251415-2-tmaimon77@gmail.comSigned-off-by: NMark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/nuvoton,npcm-pspi.txt

@@ -3,7 +3,8 @@ Nuvoton NPCM Peripheral Serial Peripheral Interface(PSPI) controller driver
 Nuvoton NPCM7xx SOC support two PSPI channels.
 
 Required properties:
- - compatible : "nuvoton,npcm750-pspi" for NPCM7XX BMC
+ - compatible : "nuvoton,npcm750-pspi" for Poleg NPCM7XX.
+				"nuvoton,npcm845-pspi" for Arbel NPCM8XX.
  - #address-cells : should be 1. see spi-bus.txt
  - #size-cells : should be 0. see spi-bus.txt
  - specifies physical base address and size of the register.