serial: Refactor mcux lpuart shim driver to use clock control interface

Refactors the mcux lpuart shim driver to use the clock control interface
instead of calling CLOCK_GetFreq() directly. This will allow SoCs with
different clock architectures to reuse this driver.

Signed-off-by: Maureen Helm <maureen.helm@nxp.com>
2 files changed