wlcore: Add support for runtime PM

wlcore: Add support for runtime PM

We can update wlcore to use PM runtime by adding functions for
wlcore_runtime_suspend() and wlcore_runtime_resume() and replacing
calls to wl1271_ps_elp_wakeup() and wl1271_ps_elp_sleep() with calls
to pm_runtime_get_sync() and pm_runtime_put().

Note that the new wlcore_runtime_suspend() and wlcore_runtime_resume()
functions are based on simplified versions of wl1271_ps_elp_sleep() and
wl1271_ps_elp_wakeup().

We don't want to use the old functions as we can now take advantage of
the runtime PM usage count. And we don't need the old elp_work at all.
And we can also remove WL1271_FLAG_ELP_REQUESTED that is no longer needed.

Pretty much the only place where we are not just converting the existing
functions is wl1271_op_suspend() where we add pm_runtime_put_noidle()
to keep the calls paired.

As the next step is to implement runtime PM autosuspend, let's not add
wrapper functions for the generic runtime PM calls. We would be getting
rid of any wrapper functions anyways.

After autoidle we should be able to start using Linux generic wakeirqs
for the padconf interrupt.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>