We have so far compiled in dt-compat only for CONFIG_SOC_SAMA5D3,
but we require it for device tree support of CONFIG_SOC_AT91SAM9
as well. Fix this.

While at it move around the obj- rules a bit to minimize the diff to
upstream.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>