ARM: dts: qcom: Add idle states device nodes for 8974/8074

Add ARM common idle states device bindings for cpuidle support for APQ
8974/8074.

Support Standalone power collapse (SPC) idle state (power down that does
not affect any SoC idle states) for each cpu.

Signed-off-by: Lina Iyer <lina.iyer@linaro.org>
Signed-off-by: Kumar Gala <galak@codeaurora.org>
Signed-off-by: Olof Johansson <olof@lixom.net>