[POWERPC] ibmebus: change probe/remove interface from using loc-code to DT path

[POWERPC] ibmebus: change probe/remove interface from using loc-code to DT path

In some cases, multiple OFDT nodes might share the same location code, so
the location code is not a unique identifier for an OFDT node. Changed the
ibmebus probe/remove interface to use the DT path of the device node instead
of the location code.

The DT path must be written into probe/remove right as it would appear in
the "devspec" attribute of the ebus device: relative to the DT root, with a
leading slash and without a trailing slash. One trailing newline will not
hurt; multiple newlines will (like perl's chomp()).

Example:

 Add a device "/proc/device-tree/foo@12345678" to ibmebus like this:
    echo /foo@12345678 > /sys/bus/ibmebus/probe

 Remove the device like this:
    echo /foo@12345678 > /sys/bus/ibmebus/remove

Signed-off-by: Joachim Fenkes <fenkes@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>