tty: rocket, remove unneeded variable

num_chan in register_PCI is used only as an alias for ports_per_aiop. So
drop num_chan and use ports_per_aiop directly.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200417105959.15201-1-jslaby@suse.cz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>