iio: adc: imx93: add four channels for imx93 adc

According to the spec, this ADC totally support 8 channels.
i.MX93 contain this ADC with 4 channels connected to pins in
the package. i.MX95 contain this ADC with 8 channels connected
to pins in the package.

Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Fixes: 7d02296ac8b8 ("iio: adc: add imx93 adc support")
Link: https://lore.kernel.org/r/20231116071026.611269-1-haibo.chen@nxp.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: imx93: Convert to platform remove callback returning void

The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is ignored (apart
from emitting a warning) and this typically results in resource leaks.
To improve here there is a quest to make the remove callback return
void. In the first step of this quest all drivers are converted to
.remove_new() which already returns void. Eventually after all drivers
are converted, .remove_new() will be renamed to .remove().

Trivially convert this driver from always returning zero in the remove
callback to the void returning variant.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20230919174931.1417681-14-u.kleine-koenig@pengutronix.de
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: imx93: fix a signedness bug in imx93_adc_read_raw()

The problem is these lines:

ret = vref_uv = regulator_get_voltage(adc->vref);
if (ret < 0)

The "ret" variable is type long and "vref_uv" is u32 so that means
the condition can never be true on a 64bit system. A negative error
code from regulator_get_voltage() would be cast to a high positive
u32 value and then remain a high positive value when cast to a long.

The "ret" variable only ever stores ints so it should be declared as
an int. We can delete the "vref_uv" variable and use "ret" directly.

Fixes: 7d02296ac8b8 ("iio: adc: add imx93 adc support")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Haibo Chen <haibo.chen@nxp.com>
Link: https://lore.kernel.org/r/Y+utEvjfjQRQo2QB@kili
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: imx93: Fix spelling mistake "geting" -> "getting"

Thrre is a spelling mistake in a dev_err_probe message. Fix it.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20230124100413.684416-1-colin.i.king@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: add imx93 adc support

The ADC in i.mx93 is a total new ADC IP, add a driver to support
this ADC.

Currently, only support one shot normal conversion triggered by
software. For other mode, will add in future.

Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Link: https://lore.kernel.org/r/20230117135137.1735536-2-haibo.chen@nxp.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>