gma500: lid_state should be __iomem

This was mostly already fixed but this one change is needed to match Kirill's
original submission

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>