spi: spidev: Add sx1301 to device tree compatibility list

Add entry for the semtech sx1301 baseband processor implementing a LoRa
concentrator IP.
At this time this chip requires an spidev userspace driver.

Signed-off-by: Ben Whitten <ben.whitten@lairdtech.com>
Signed-off-by: Steve deRosier <derosier@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>