drm/i915/gen9+: Enable hotplug detection early

drm/i915/gen9+: Enable hotplug detection early

BugLink: http://bugs.launchpad.net/bugs/1675032
commit 2a57d9cce1c08578097d965468e37f06d71fa495 upstream.

For LSPCON resume time initialization we need to sample the
corresponding pin's HPD level, but this is only available when HPD
detection is enabled. Currently we enable detection only when enabling
HPD interrupts which is too late, so bring the enabling of detection
earlier.

This is needed by the next patch.

Cc: Shashank Sharma <shashank.sharma@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1485509961-9010-2-git-send-email-imre.deak@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
(rebased onto v4.10.4 due to missing s/IS_BROXTON/IS_GEN9_LP/ upstream change)
(corrected stable tag)
Signed-off-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>