arm: kirkwood: use the default of match table

mach-kirkwood/board-dt.c defines its own OF matching table, but in
fact, it is the same to the default of_default_bus_match_table[] which
is already used by mach-mvebu, mach-dove and mach-orion5x.

This patch therefore makes mach-kirkwood use the same default OF
matching table.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>