drivers: adc: stm32: Add STM32h7xx linearity calibration

The STM32H7 series has a special ADC, which is calibrated
on the factory. The calibration values are stored in flash
and must be retrieved upon powering up the device.

Failure to calibrate the device leads to missing codes in
the ADC readings.

Fixes #35529

Signed-off-by: Lasse Sangild <lsangild@gmail.com>