drm/i915: Move the .global_resources() hook call into modeset_update_crtc_power_domains()

We may need to access various hardware bits in the .global_resources()
hook, so move the call to occur after enabling all the newly required
power wells, but before disabling all the now unneeded wells. This
should guarantee that we have all the sufficient hardware resources
available during the .global_resources() call. And if not, any additional
resources must be explicitly acquired by the .global_resorces() hook.

For instance on VLV/CHV we need to access the gunit mailbox so that we
can talk to punit/cck over sideband. In addition some PFI credit
reprogramming may need to be addes as well, which may require the disp2d
well.

This should also make the power domain refcounts consistent on platforms
which don't have a .global_resource() hook since now they too will
call modeset_update_crtc_power_domains() which will drop the init power.
Previously init power was just left enabled for such platforms.

Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>