drm/i915/hpd: Add support for blocking the IRQ handling on an HPD pin

drm/i915/hpd: Add support for blocking the IRQ handling on an HPD pin

Add support for blocking the IRQ handling on the HPD pin of a given
encoder, handling IRQs that arrived while in the blocked state after
unblocking the IRQ handling. This will be used by a follow-up change,
which blocks/unblocks the IRQ handling around DP link training.

This is similar to the intel_hpd_disable/enable() functionality, by also
handling encoders/ports with a pulse handler (i.e. also
blocking/unblocking the short/long pulse handling) and handling the IRQs
arrived in the blocked state after the handling is unblocked (vs. just
dropping such IRQs).

v2:
- Handle encoders without a port assigned to them.
- Fix clearing IRQs from intel_hotplug::short_port_mask.
v3:
- Rename intel_hpd_suspend/resume() to intel_hpd_block/unblock(). (Jani)
- Refer to HPD pins as hpd_pin vs. hpd.
- Flush dig_port_work in intel_hpd_block() if any encoder using the HPD
  pin has a pulse handler.
v4:
- Fix hpd_pin_has_pulse(), checking the encoder's HPD pin.
v5:
- Rebase on port->hpd_pin tracking. (Ville)
v6: (Jani)
- Add hpd_pin_is_blocked() helper.
- Use the hpd_pin_mask term for a mask of pins instead of hpd_pins.
- Prevent decrementing a 0 refcount in unblock_hpd_pin().

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250305114820.3523077-1-imre.deak@intel.com