[POWERPC] Fix Pegasos keyboard detection

As of 2.6.22 the kernel doesn't recognize the i8042 keyboard/mouse
controller on the PegasosPPC.  This is because of a feature/bug in the
OF device tree: the "device_type" attribute is an empty string instead
of "8042" as the kernel expects.  This adds a secondary detection
which looks for a device whose *name* is "8042" if there is no device
whose *type* is "8042".

Signed-off-by: Alan Curry <pacman@world.std.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>