serial: imx: set receiver level before starting uart

serial: imx: set receiver level before starting uart

Set the receiver level to something > 0 before calling imx_uart_start_rx
in rs485_config. This is necessary to avoid an interrupt storm that
might prevent the system from booting. This was seen on an i.MX7 device
when the rs485-rts-active-low property was active in the device tree.

Fixes: 6d215f83e5fc ("serial: imx: warn user when using unsupported configuration")
Cc: stable <[email protected]>
Signed-off-by: Stefan Eichenberger <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>