Final version of the patch that adds support for RS485 communications to the atmel_serial driver.

The patch has been already sent and discussed on both linux-kernel and linux-arm-kernel mailing lists several times.

Many people collaborated to improve and test the code:
Tested-by: NSebastian Heutling <Sebastian.Heutling@who-ing.de>
Tested-by: NBernhard Roth <br@pwrnet.de>
Reviewed-by: NRyan Mallon <ryan@bluewatersys.com>
Signed-off-by: NClaudio Scordino <claudio@evidence.eu.com>
Signed-off-by: NMichael Trimarchi <michael@evidence.eu.com>
Signed-off-by: NRick Bronson <rick@efn.org>
Signed-off-by: NSebastian Heutling <Sebastian.Heutling@who-ing.de>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>