drivers: sensor: ina23x: fix sample fetching

Fix the usage of sensor shell module that calls sensor_sample_fetch
function with SENSOR_CHAN_ALL id which is not supported and
causes the following error:

uart:~$ sensor get INA237 current
Failed to read sensor: -134
channel idx=31 current =   0.000000

Fix that by adding support for SENSOR_CHAN_ALL channel id.

Signed-off-by: Bartosz Bilas <b.bilas@grinn-global.com>