Add runtime PM core support to davinci by using the pm_clk
infrastructure of the PM core.

When runtime PM is enabled, the davinci runtime PM implementation will
use the pm_clk layer to enable/disable clocks on demand.  When runtime
PM is disabled, the pm_clk core will automatically enable clocks when
the driver is bound and disable clocks when the driver is unbound.

Cc: Mark A. Greer <mgreer@animalcreek.com>
Cc: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>
[nsekhar@ti.com: pruned list of header file includes and removed some
debug code]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>