arm: ecard: use dev_groups and not dev_attrs for bus_type

The dev_attrs field has long been "depreciated" and is finally being
removed, so move the driver to use the "correct" dev_groups field
instead for struct bus_type.

Cc: Russell King <linux@armlinux.org.uk>
Cc: <linux-arm-kernel@lists.infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>