Detecting reset reason is, in some cases, a destructive operation and
in such cases it is impossible to obtain that information in the
kernel without some help from barebox.

Pass reset source and reset source instance to kernel to Linux to make
it availible to Linux userspace. This info is placeed under
/chosen/bootsource and it can be read under Linux in

/sys/firmware/devicetree/base/chosen/reset-source.

and

/sys/firmware/devicetree/base/chosen/reset-source-instance.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>