Added doxygen comments

modified files
#	modified:   include/vdev.h
#	modified:   trap.c
#	modified:   trap.h
#	modified:   vdev/vdev_gicd.c
#	modified:   vdev/vdev_gicd.h
#	modified:   vdev/vdev_timer.c
#	modified:   vdev/vdev_timer.h