iio: adc: at91: don't use the last converted data register
iio: adc: at91: don't use the last converted data register

If touchscreen mode is enabled and a conversion is requested on another
channel, the result in the last converted data register can be a
touchscreen relative value. Starting a conversion involves to do a
conversion for all active channel. It starts with ADC channels and ends
with touchscreen channels. Then if ADC_LCD register is not read quickly,
its content may be a touchscreen conversion.
To remove this temporal constraint, the conversion value is taken from
the channel data register.

Signed-off-by: Ludovic Desroches <627575320a9526cb6c91021c9940202b0e84c416@atmel.com>
Acked-by: Alexandre Belloni <a7228e626ecf0022ac91fc1cd8db88e71d0e5e0e@free-electrons.com>
Acked-by: Nicolas Ferre <45b517be0e5ec6dc3a39715767c1d18e090d39b4@atmel.com>
Cc: d96e5b2dd07c1733b2b013bd82922c22baade37d@vger.kernel.org
Signed-off-by: Jonathan Cameron <09f65b71b7655725897b2fd41a09a0cefe2e1ace@kernel.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs