imx9: imx93_evk: add low drive mode support on 11x11 EVK

imx9: imx93_evk: add low drive mode support on 11x11 EVK

Add a static u-boot config for i.MX93 low drive mode support. When
low drive mode is enabled, VDD_SOC is set to 0.75V. Bus clocks,
A55 core clock (900Mhz), DDR clock (1866MTS), and some peripherals
clocks (USDHC/FLEXSPI/PDM/DISP_PIX/CAM_PIX) must decrease to meet
max frequencies in low drive mode.

Also set standby voltage for buck1

Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>