spi: add mt8186-nor compatible string

Add MT8186 spi-nor controller support.
MT8186 needs a new clock name, axi_s, for spi nor axi slave bus clock.
Signed-off-by: Guochun Mao <guochun.mao@mediatek.com>
Signed-off-by: Zhen Zhang <zhen.zhang@mediatek.com>
Link: https://lore.kernel.org/r/20220118142820.2729-2-guochun.mao@mediatek.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/mediatek,spi-mtk-nor.yaml

@@ -30,6 +30,7 @@ properties:
               - mediatek,mt7622-nor
               - mediatek,mt7623-nor
               - mediatek,mt7629-nor
+              - mediatek,mt8186-nor
               - mediatek,mt8192-nor
               - mediatek,mt8195-nor
           - enum:
@@ -49,6 +50,8 @@ properties:
       - description: clock used for controller
       - description: clock used for nor dma bus. this depends on hardware
                      design, so this is optional.
+      - description: clock used for controller axi slave bus.
+                     this depends on hardware design, so it is optional.
 
   clock-names:
     minItems: 2
@@ -56,6 +59,7 @@ properties:
       - const: spi
       - const: sf
       - const: axi
+      - const: axi_s
 
 required:
   - compatible