ARM: shmobile: R-Mobile: Add DT support for PM domains

ARM: shmobile: R-Mobile: Add DT support for PM domains

Populate the PM domains from DT, and provide support to hook up devices
to their respective PM domain.

The always-on power area (e.g. C5 on r8a7740) is created as a PM domain
without software control, to allow Run-Time management of module clocks
for hardware blocks inside this area.

Special cases like PM domains containing CPUs, the console device, or
Coresight-ETM, are handled by scanning the DT topology.

As long as the ARM debug/perf code doesn't use resource management with
runtime PM support, the power area containing Coresight-ETM (e.g. D4 on
r8a7740) must be kept powered to avoid a crash during resume from s2ram
(dbg_cpu_pm_notify() calls reset_ctrl_regs() unconditionally, causing an
undefined instruction oops).

Initialization is done from core_initcall(), as the
"renesas,intc-irqpin" driver uses postcore_initcall().

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>