ARM: dts: Only build dtb if associated Arch and/or SoC is enabled

A number of arches (EXYNOS/IMX/TEGRA) are separated out into finer grained
definitions whether it be sub ARCH or SOC definitions. The device tree blobs
should only be built if the specific option is enabled that supports that
device or it might be that there's an expectation that the device is supported
when in actual fact it's not. This ensures only the relevant bits are built.

Also standardised the line break between the arch/soc definitions and the
dtbs to be on separate lines for better consistency as per feedback.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Thierry Reding <treding@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Shawn Guo <shawn.guo@freescale.com>
[olof: Fixed stray \ in one of the IMX rules]
Signed-off-by: Olof Johansson <olof@lixom.net>