LED: Fix missing semicolon in OF documentation

Trivial fix

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Rob Landley <rob@landley.net>
Cc: devicetree-discuss@lists.ozlabs.org
Cc: linux-doc@vger.kernel.org
Signed-off-by: Rob Herring <rob.herring@calxeda.com>