Staging: ipack: remove pr_fmt definition.

As there is no pr_* function used here, pr_fmt is not needed.

Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>