state of the GPIO line is.  On some systems the LEDs are put into some
state by the firmware or hardware before Linux boots, and it is desired to
have them keep this state which is otherwise unknown to Linux.

This requires that the underlying GPIO driver support reading the value of
output GPIOs.  Some drivers support this and some do not.

The platform device binding gains a field in the platform data
"default_state" that controls this.  There are three constants defined to
select from on, off, or keeping the current state.  The OpenFirmware
binding uses a property named "default-state" that can be set to "on",
"off", or "keep".  The default if the property isn't present is off.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Sean MacLennan <smaclennan@pikatech.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>