ARM: dts: OMAP2+: Use #include for all device trees

Replace /include/ by #include for OMAP2+ DT, in order to use the
C pre-processor, making use of #define features possible.

Signed-off-by: Florian Vaussard <florian.vaussard@epfl.ch>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Benoit Cousson <benoit.cousson@linaro.org>