drm/i915: fix DDI PLLs HW state readout code

commit 0882dae983707455e97479e5e904e37673517ebc upstream.

Properly zero the refcounts and crtc->ddi_pll_set so the previous HW
state doesn't affect the result of reading the current HW state.

This fixes WARNs about WRPLL refcount if we have an HDMI monitor on
HSW and then suspend/resume.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=64379


Tested-by: Qingshuai Tian <qingshuai.tian@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>