USB: Staging: media: lirc: lirc_imon: 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: Jarod Wilson <jarod@wilsonet.com>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>