board: phytec: phycore-imx93: Fix i.MX93 voltage modes

board: phytec: phycore-imx93: Fix i.MX93 voltage modes

Fix support for i.MX93 voltage modes on phyCORE-i.MX93 SoM boards.

First of all, Kconfig option CONFIG_IMX9_LOW_DRIVE_MODE is gone since
commit c9efcad23741 ("imx93_evk: Remove CONFIG_IMX9_LOW_DRIVE_MODE and
ld defconfig") and was replaced by runtime detection mechanism. Thus
lets use is_voltage_mode() instead of Kconfig to detect CPU type and
select proper voltage mode.

Secondly, 1400MHz ND mode (Nominal Drive) requiring 0.85V BUCK voltage
was not supported with current power_init_board() PMIC settings. Add
check also for this CPU type and set BUCK voltage accordingly.

Last but not least, add printf() printouts about PMIC voltage mode to
the console. This makes it more apparent and verbose about voltage mode
in use. Also our internal tests depend on this printout to catch issues
with i.MX93 CPU types and set PMIC voltage modes.

Signed-off-by: Primoz Fiser <primoz.fiser@norik.com>