[ARM] 5337/1: gumstix: move am200 specific gpio pins into am200epd.

The gpio setup for AM200 specific GPIO pins should be done in the AM200
code rather than in generic gumstix code.

Signed-off-by: Jaya Kumar <jayakumar.lkml@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>