iio: proximity: lidar: optimize i2c transactions

Optimize device tranactions using i2c transfers versus multiple
possibly racey i2c_smbus_* function calls, and only one transaction
for distance measurement. Falls back to smbus method if i2c
functionality isn't available.

Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>