feat(nxp-clk): enable UART clock

Before this change, the internal oscillator clocked the UART with a
frequency of 48MHz. With the necessary support added, the UART clock
rate is increased to 125MHz by changing the clock source from FIRC to
PERIPH PLL PHI3.

Change-Id: I3160dc6860ebf441c9bea8eaf9d8d12de48bd647
Signed-off-by: Ghennadi Procopciuc <ghennadi.procopciuc@nxp.com>
4 files changed