Bug#770212: add automatic stdout-path console for of platforms

[Leif Lindholm <leif.lindholm@linaro.org>]

X-Debbugs-CC: ijc@debian.org
Package: src:linux
Version: 3.16.7
Severity: wishlist

Linux 3.17 gained support for using a device-tree provided default
console, from the ePAPR 1.1 'stdout-path' property. This removes the
need for explicitly passing a console= parameter to pick the
appropriate console for your average ARM system.

I have verified that the two following two upstream commits, imported
to the linux-3.16.7 tree, respects this property and enables output to
the correct device.
a208ffd251d08ed7ba6bdf3ae1e423373fb12d3d
(of: Enable console on serial ports specified by /chosen/stdout-path)
and
3482f2c52b77bf6596e24aae82e204a0603eba66
(of: Create of_console_check() for selecting a console specified in
/chosen)

Enabling this for Jessie would also enable the arm and arm64
debian-installers to require fewer special runes.