drm/i915/dp: Disable unnecessary HPD polling for eDP

A registered eDP connector is considered to be always connected, so it's
unnecessary to poll it for a connect/disconnect event. Polling it
involves AUX accesses toggling the panel power, which in turn can
generate a spurious short HPD pulse and possibly a new poll cycle via
the short HPD handler runtime resuming the device. Avoid this by
disabling the polling for eDP connectors.

This avoids IGT tests timing out while waiting for the device to runtime
suspend, the timeout caused by the above runtime resume->poll->suspend->
resume cycle keeping the device in the resumed state.

Testcase: igt/kms_pm_rpm/unverisal-planes
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241009194358.1321200-3-imre.deak@intel.com