tty: serial: fsl_lpuart: only enable Idle Line Interrupt for non-dma case

For the lpuart driver, the Idle Line Interrupt Enable now is only needed
for the CPU mode, so enable the UARTCTRL_ILIE at the correct place, and
clear it when shutdown.

Also need to configure the suitable UARTCTRL_IDLECFG, now the value is
0x7, represent 128 idle characters will trigger the Idle Line Interrupt.

Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Link: https://lore.kernel.org/r/20221125101953.18753-2-sherry.sun@nxp.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>