With 'dx' equal to 0.625V and 15 bit ADC, calculations overflow
when difference against GND is ~20% of the ADC range. Fix this.
Signed-off-by: NIvan T. Ivanov <ivan.ivanov@linaro.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

The voltage ADC is peripheral of Qualcomm SPMI PMIC chips. It has
15bits resolution and register space inside PMIC accessible across
SPMI bus.

The vadc driver registers itself through IIO interface.
Signed-off-by: NStanimir Varbanov <svarbanov@mm-sol.com>
Signed-off-by: NIvan T. Ivanov <iivanov@mm-sol.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>