spi_nxp_lpspi: Fix faulting register access

On some platforms, the module is not getting clocked until call to
LPSPI_MasterInit, this will be fixed soon with upcoming update to native
driver and will clock the module in driver init instead of start of
transfer, but for now, move this code within the condition check that
already exists for this purpose.

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>