ARM: dts: DRA7: Add bandgap and related thermal nodes

Add bandgap and related thermal nodes. The patch adds 5 thermal
sensors. Only one cooling device for mpu as of now. The sensors are
the exact same on both dra72 and dra7. Introduce CPU, GPU, core nodes
for the moment as they are direct reuse of OMAP5 entities.

NOTE: OMAP4 has a finer counter granularity, which allows for a delay
of 1000ms in the thermal zone polling intervals. DRA7 have different
counter mechanism, which allows at maximum a 500ms timer. Adjust the
cpu thermal zone accordingly for DRA7.

Signed-off-by: Keerthy <j-keerthy@ti.com>
[t-kristo@ti.com: few reuse from OMAP5 entities]
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>