dt-bindings: hwmon: Fix incorrect $id paths

Fix the path warnings in the adi,axi-fan-control and adt7475 bindings:

Documentation/devicetree/bindings/hwmon/adt7475.yaml: $id:
  relative path/filename doesn't match actual path or filename
  expected: http://devicetree.org/schemas/hwmon/adt7475.yaml#
Documentation/devicetree/bindings/hwmon/adi,axi-fan-control.yaml: $id:
  relative path/filename doesn't match actual path or filename
  expected: http://devicetree.org/schemas/hwmon/adi,axi-fan-control.yaml#

Cc: Jean Delvare <jdelvare@suse.com>
Cc: linux-hwmon@vger.kernel.org
Acked-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Rob Herring <robh@kernel.org>