tty: serial: OMAP: ensure FIFO levels are set correctly in non-DMA mode

tty: serial: OMAP: ensure FIFO levels are set correctly in non-DMA mode

Ensure FIFO levels are set correctly in non-DMA mode (the default).
This patch will cause a receive FIFO threshold interrupt to be raised when
there is at least one byte in the RX FIFO.  It will also cause a transmit
FIFO threshold interrupt when there is only one byte remaining in the TX
FIFO.

These changes fix the receive interrupt problem and part of the
transmit interrupt problem.  A separate set of issues must be worked
around for the transmit path to have a basic level of functionality; a
subsequent patch will address these.

DMA operation is unaffected by this patch.

Signed-off-by: Paul Walmsley <[email protected]>
Cc: Tomi Valkeinen <[email protected]>
Cc: Govindraj Raja <[email protected]>
Cc: Kevin Hilman <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>