OF: Add helper for matching against linux,stdout-path

OF: Add helper for matching against linux,stdout-path

devicetrees may have a linux,stdout-path property in the chosen
node describing the console device. This adds a helper function
to match a device against this property so a driver can call
add_preferred_console for a matching device.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 5c19e95216b93b0d29c6a4887e69a980edc6fc81)
Signed-off-by: Mark Brown <broonie@linaro.org>