drivers: adc: stm32: resolution rework

Rework the way to set the STM32 ADC resolution.
Instead of using special macros in device tree, supported resolutions are
now simply listed as an array.

From this array, the driver defines two tables. The first contains the same
values as the array, the second contains the LL macros for each resolution.
When setting the resolution, the driver checks the value with the first
table, then sets it with the second table.

The two tables are defined for each enabled ADC instance so there are no
conflicts if different ADC have different resolutions.

For STM32H7, this changes the internal values used for 14 and 12-bit
resolutions, from 0b101/110 to 0b001/010 respectively, i.e. it uses the
so-called "legacy" resolutions instead of the "power-optimized" ones.
Note that AN5354 indicates: "The optimized modes have better power
consumption figures. The standard modes have better parameters, but
power consumption is not optimized and is comparable to 16-bit mode."

Signed-off-by: Guillaume Gautier <guillaume.gautier-ext@st.com>