drm/i915: fix SDEIMR assertion when disabling LCPLL

This was causing WARNs in one machine, so instead of trying to guess
exactly which hotplug bits should exist, just do the test on the
non-HPD bits. We don't care about the state of the hotplug bits, we
just care about the others, that need to be 1.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>