arm: dts: apq8064: Add thermal zones, tsens and qfprom nodes

TSENS is part of GCC, hence add TSENS properties as part of GCC node.
Also add thermal zones and qfprom nodes.
Update GCC bindings doc to mention the possibility of optional TSENS
properties that can be part of GCC node.

Acked-by: Eduardo Valentin <edubezval@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>