Revert "serial: omap: fix software flow control"

This reverts commit 957ee727
(serial: omap: fix software flow control).

As Russell has pointed out, that commit isn't fixing
Software Flow Control at all, and it actually makes
it even more broken.

It was agreed to revert this commit and use Russell's
latest UART patches instead.

Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>