dt-bindings: memory-controllers: narrow regex for unit address to hex numbers

Regular expression used to match the unit address part should not allow
non-hex numbers.
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Link: https://lore.kernel.org/r/20240123083517.21091-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Documentation/devicetree/bindings/memory-controllers/nvidia,tegra20-emc.yaml

@@ -145,7 +145,7 @@ patternProperties:
   "^emc-table@[0-9]+$":
     $ref: "#/$defs/emc-table"
 
-  "^emc-tables@[a-z0-9-]+$":
+  "^emc-tables@[a-f0-9-]+$":
     type: object
     properties:
       reg: