ARM: dts: omap4-droid4: update touchscreen

Update the Droid 4 devicetree to properly describe the reset
GPIO. Also rename the node to touchscreen instead of tsp,
which seems to be commonly used for touchscreens.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>