dt-bindings: vendor-prefixes: Clarify Macronix prefix

When looking at compatible prefixes, Macronix is sometimes referred as
"mxicy":
- mxicy,mx25r1635f
- mxicy,mx25u6435f
- mxicy,mx25v8035f
- mxicy,mx25f0a-spi
and sometimes as "mxic":
- mxic,multi-itfc-v009-nand-controller
- mxic,enable-randomizer-otp

The oldest prefix that is also the one preferred by Macronix engineers
is "mxicy", so document the other one and mark it deprecated.
Signed-off-by: NMiquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Link: https://lore.kernel.org/linux-mtd/20211216111654.238086-7-miquel.raynal@bootlin.com

Documentation/devicetree/bindings/vendor-prefixes.yaml

@@ -802,6 +802,9 @@ patternProperties:
     description: Mundo Reader S.L.
   "^murata,.*":
     description: Murata Manufacturing Co., Ltd.
+  "^mxic,.*":
+    description: Macronix International Co., Ltd.
+    deprecated: true
   "^mxicy,.*":
     description: Macronix International Co., Ltd.
   "^myir,.*":