Previously, packets that have been dumped are shown in the
kernel log like this:

drivers/input/joystick/iforce/iforce-packets.c: info cmd = ff04, data =
56
02
04
00

Use dev_dbg to dump the packages only when requested and to list
the parent device as well. Use printf logic to generate the hexdump
instead of looping through every char that needs to be printed (which
in turn fixes the unnecessary newlines and looks more clean in general).

The resulting package dump output does now look like this:

usb 2-8: iforce_dump_packet info cmd = ff04, data = 56 02 04 00
Signed-off-by: Tim Schumacher <timschumi@gmx.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>