imxrt:Clock config fixes and board.h sets sources and divisors
* imxrt:clockconfig bug fix & Board config set clocks
Fixed logic that was not clearing bits as ~ was
mising in &= mask operations.
Use valuse from the board.h file so set the Mux that
selects the clock sources.
Use board defined PODF values to select clock.
Only configure USDHC2 clocks when board defines clocks.
* imxrt1050-evk:Board setting used to set LSPI and USDHC Clocks
Approved-by: GregoryN <gnutt@nuttx.org>