soc: nxp mcxc: Add tpm clock selection

Timer/PWM Module (TPM) initial clock source is not selected.
Add initial clock source selection based on Devicetree configuration.
Rename clock sources definitions from LPUART specific to general names
usable by several modules on the SoC.

Signed-off-by: Michal Smola <michal.smola@nxp.com>