soc: mcxc: Set LPUART1 clock source from clock_init

The clock source for LPUART0 for the MCXC family is already
initialized in the corresponding soc.c -> clock_init().
Initialization for LPUART1 is missing. This is however
necessary if a user wants to configure LPUART1 as the default
console output.

Signed-off-by: Maximilian Werner <maximilian.werner96@gmail.com>