iio: Add driver for Infineon DPS310

The DPS310 is a temperature and pressure sensor. It can be accessed over
i2c and SPI, but this driver only supports polling over i2c.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>