media: v4l-ioctl: Fix typo on v4l_print_frmsizeenum

max_width and max_height are swap with step_width and step_height.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>