i2c: nomadik: Fixup deployment of runtime PM

Since the runtime PM state is expected to be active according to the
amba bus, we must align our behaviour while probing to it.

Moreover, this is needed to be able to have the driver fully functional
without depending on CONFIG_RUNTIME_PM.

Since the device is active while a successful probe has been completed,
the reference counting for the clock will be screwed up and never reach
zero. We resolve this by implementing runtime PM callbacks and let them
handle the resources accordingly, including the clock.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
[wsa: s/#if/#ifdef/]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>