Make lid switch edge rather than level triggered.

Right now, because of the way that configurations are applied, when
the display turns on because of an incoming phone call the fact that
the lid is "shut" will automatically put the phone back to sleep,
causing the ringer to be silenced. By making this edge triggered, the
display will only sleep or wake up when the lid is initially shut or
opened, respectively, avoiding this issue. In the future we may want
to revise this so that the lid-shut state is better understood
throughout the system to avoid these types of issues, but for now
this is sufficient.

Bug: 26600446
Change-Id: I10d403b62944ed6eceaff58cddad5c243a2884df