soc: mxrt10xx: Update the clock init code

1. Setup VDD_SOC with the appropriate setting
   depending on the SoC
2. Do not configure PLL_SYS and PLL_USB. These
   are already configured by the ROM code using
   the DCD
3. Fix setting for USDHC clock

Signed-off-by: Mahesh Mahadevan <mahesh.mahadevan@nxp.com>