drivers: base: Port power management code from Linux ...

Port an extremely abridged version of power management/power domain
code from Linux as a dependency of i.MX7D PCIe work. Currenlty only
bare minimum of functionality is implemented.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>