ARM: dts: n900: Rename isp1704 to isp1707 to match correct name

This change does not break existing userspace or Maemo software because
isp1704_charger.c always export power supply device under isp1704 name.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>