drivers: uart_mcux_lpuart: Handle multiple uart case

Handle the case where there are multiple different kinds of UART on one
platform, the other UART driver select SERIAL_SUPPORT_ASYNC but LPUART
did not, causing build error in LPUART driver. Shield LPUART driver from
this case by introducing driver config to indicate that in fact LPUART
is the one enabling ASYNC.

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