ARM: dts: imx6dl-b1x5v2: drop unsupported vcc-supply for MPL3115A2

The MPL3115A2 I2C pressure sensor driver does not take a VCC regulator.
The bindings are so far trivial, but the datasheet does not have a VCC
pin.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>