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 <[e-mail]>
Fixes: 7d02296ac8b8 ("iio: adc: add imx93 adc support")
Link: https://lore.kernel.org/r/[e-mail]
Cc: <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/imx93_adc.c

···
 	IMX93_ADC_CHAN(1),
 	IMX93_ADC_CHAN(2),
 	IMX93_ADC_CHAN(3),
+	IMX93_ADC_CHAN(4),
+	IMX93_ADC_CHAN(5),
+	IMX93_ADC_CHAN(6),
+	IMX93_ADC_CHAN(7),
 };
 
 static void imx93_adc_power_down(struct imx93_adc *adc)