regulator: arizona-micsupp: Fix choosing selector in arizona_micsupp_map_voltage

If min_uV is in the range of: 3250001~3269999,
current code uses the equation:
        selector = DIV_ROUND_UP(min_uV - 1700000, 50000);
Then selector will be 32.
Then arizona_micsupp_list_voltage returns -EINVAL for this case which is wrong.

This patch fixes this issue:
If min_uV > 3200000, selector should be ARIZONA_MICSUPP_MAX_SELECTOR.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>