drivers: clock_control: npcx: add MCLKD as i3c source clock

1. The only valid values of MCLKD clock frequency
   are between 40Mhz to 50Mhz.
2. If DMA is used, the APB4_CLK clock frequency must
   be equal to or higher than 20Mhz.

Signed-off-by: Alvis Sun <yfsun@nuvoton.com>