OMAP1: AMS_DELTA: add modem support

This patch adds support for modem device found on Amstrad E3 (Delta) board.

Based on earlier patch by Jonathan McDowell, available at
http://the.earth.li/pub/e3/2.6.19/ams-delta-modem.patch.
Modified after Ladislav Michl's arch/arm/mach-omap1/board-voiceblue.c.

This patch is dependent on 8250 driver changes getting accepted upstream:
http://git.kernel.org/?p=linux/kernel/git/sfr/linux-next.git;a=commit;h=7053133124d5cdf207c1168c7a0c582a18e12ea7

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Signed-off-by: Tony Lindgren <tony@atomide.com>