USB: iowarrior.c: remove err() usage

err() was a very old USB-specific macro that I thought had
gone away.  This patch removes it from being used in the
driver and uses dev_err() instead.

CC: Rusty Russell <rusty@rustcorp.com.au>
CC: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
CC: Mauro Carvalho Chehab <mchehab@redhat.com>
CC: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>