tty: serial: fsl_lpuart: set receive watermark for imx8qxp platform

Since imx8qxp RX FIFO depth is 64 datawords, it will be better to set
the rx watermark as 31, which means when the number of datawords in the
receive FIFO(>= 32) is greater than the watermark, an interrupt or a DMA
request is generated.
Also keep the console rx watermark as 1 to make sure it responsive.

Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Link: https://lore.kernel.org/r/20230130064449.9564-3-sherry.sun@nxp.com


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