tegra, serial8250: add ->handle_break() uart_port op

The "KT" serial port has another use case for a "received break" quirk,
so before adding another special case to the 8250 core take this
opportunity to push such quirks out of the core and into a uart_port op.

Stephen says:
"If the callback function is to no longer live in 8250.c itself,
 arch/arm/mach-tegra/devices.c isn't logically a good place to put it,
 and that file will be going away once we get rid of all the board files
 and move solely to device tree."

...so since 8250_pci.c houses all the quirks for pci serial devices this
quirk is similarly housed in of_serial.c.  Once the open firmware
conversion completes the infrastructure details
(include/linux/of_serial.h, and the export) can all be removed to make
this self contained to of_serial.c.

Cc: Nhan H Mai <nhan.h.mai@intel.com>
Cc: Colin Cross <ccross@android.com>
Cc: Olof Johansson <olof@lixom.net>
[stephen: kill CONFIG_SERIAL_TEGRA in favor just using CONFIG_ARCH_TEGRA]
Cc: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Sudhakar Mamillapalli <sudhakar@fb.com>
Reported-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/of_serial.h

@@ -0,0 +1,17 @@
+#ifndef __LINUX_OF_SERIAL_H
+#define __LINUX_OF_SERIAL_H
+
+/*
+ * FIXME remove this file when tegra finishes conversion to open firmware,
+ * expectation is that all quirks will then be self-contained in
+ * drivers/tty/serial/of_serial.c.
+ */
+#ifdef CONFIG_ARCH_TEGRA
+extern void tegra_serial_handle_break(struct uart_port *port);
+#else
+static inline void tegra_serial_handle_break(struct uart_port *port)
+{
+}
+#endif
+
+#endif /* __LINUX_OF_SERIAL */