HID: hid-core: convert to use DRIVER_ATTR_RO and drv_groups

In the quest to get rid of DRIVER_ATTR(), this patch converts the
hid-core code to use DRIVER_ATTR_RO() and also moves to use drv_groups
as creating individual sysfs files is not good (it races with userspace
notifications.)

Cc: Jiri Kosina <jikos@kernel.org>
Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: <linux-input@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>