tty: serial: fsl_lpuart: make rx_watermark configurable for different platforms

tty: serial: fsl_lpuart: make rx_watermark configurable for different platforms

BugLink: https://bugs.launchpad.net/bugs/2033931
[ Upstream commit 34ebb26f12a84b744f43c5c4869516f122a2dfaa ]

Add rx_watermark parameter for struct lpuart_port to make the receive
watermark configurable for different platforms.
No function changed.

Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Link: https://lore.kernel.org/r/20230130064449.9564-2-sherry.sun@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: a82c3df955f8 ("tty: serial: fsl_lpuart: reduce RX watermark to 0 on LS1028A")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>