[POWERPC] Add a check for keyboard/mouse device nodes in check_legacy_ioport()

The device tree for the MPC8641 HPCN does not implement the device type
property for I8042 nodes.

In addition to checking the I8042 node's device type, also match the
keyboard and/or mouse nodes' compatible property.

Signed-off-by: Wade Farnsworth <wfarnsworth@mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>