Fix IP alignment problem

This patch removes volatile from:
volatile IP_t *ip = (IP_t *)xip;

Due to a bug, avr32-gcc will assume that ip is aligned on a word boundary when
using volatile, which causes an exception since xip isn't aligned on a word
boundary.

Signed-off-by: Gunnar Rangoy <gunnar@rangoy.com>
Signed-off-by: Paul Driveklepp <pauldriveklepp@gmail.com>
Signed-off-by: Olav Morken <olavmrk@gmail.com>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>