[ARM] 3571/1: netX: serial driver for Hilscher netX

Patch from Sascha Hauer

This patch adds the serial driver for Hilscher's netX network
processors.

Signed-off-by: Robert Schwebel <r.schwebel@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>