ARM: dts: imx7d-sdb: Add support for mpl3115 sensor

The i.MX 7D SDB has a MPL3115 Pressure sensor.
Add support for this sensor, which is included in the trivial i2c devices
and according to the bindings documentation, just need a compatible field
and an address.

Signed-off-by: Marco Franchi <marco.franchi@nxp.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>