power/supply: unify DT documentation

Currently the power supply device tree documentation is spread
in .../bindings/power_supply and .../bindings/power. This
unifies the files for chargers and battery fuel gauges in
.../bindings/power/supply and the ones for system reset/shutdown
in .../bindings/power/reset (same structure as used for the
drivers itself).

Signed-off-by: Sebastian Reichel <[e-mail]>

MAINTAINERS

···
 L:	[e-mail]
 T:	git git://git.infradead.org/battery-2.6.git
 S:	Maintained
-F:	Documentation/devicetree/bindings/power/
-F:	Documentation/devicetree/bindings/power_supply/
+F:	Documentation/devicetree/bindings/power/supply/
 F:	include/linux/power_supply.h
 F:	drivers/power/supply/