iio: accel: hid-sensor-accel-3d: Fix duplicate scan index error

When both accel_3d and gravity sensor are present, iio_device_register()
fails with "Duplicate scan index" error.
The reason for this is setting of indio_dev->num_channels based on
accel_3d channel for both gravity and accel-3d sensor. But number of
channels are not same, so for gravity it is pointing to some invalid
memory and getting scan_index to compare which may match.
To fix this issue, set the indio_dev->num_channels correctly based on
the sensor type.

Fixes: 0e377f3b9ae9 ('iio: Add gravity sensor support')
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/accel/hid-sensor-accel-3d.c

@@ -370,10 +370,12 @@ static int hid_accel_3d_probe(struct platform_device *pdev)
 		name = "accel_3d";
 		channel_spec = accel_3d_channels;
 		channel_size = sizeof(accel_3d_channels);
+		indio_dev->num_channels = ARRAY_SIZE(accel_3d_channels);
 	} else {
 		name = "gravity";
 		channel_spec = gravity_channels;
 		channel_size = sizeof(gravity_channels);
+		indio_dev->num_channels = ARRAY_SIZE(gravity_channels);
 	}
 	ret = hid_sensor_parse_common_attributes(hsdev, hsdev->usage,
 					&accel_state->common_attributes);
@@ -395,7 +397,6 @@ static int hid_accel_3d_probe(struct platform_device *pdev)
 		goto error_free_dev_mem;
 	}
 
-	indio_dev->num_channels = ARRAY_SIZE(accel_3d_channels);
 	indio_dev->dev.parent = &pdev->dev;
 	indio_dev->info = &accel_3d_info;
 	indio_dev->name = name;