drm/i915/gen9bc: Handle TGP PCH during suspend/resume

For Legacy S3 suspend/resume GEN9 BC needs to enable and
setup TGP PCH.

v2:
* Move Wa_14010685332 into it's own function - vsyrjala
* Add TODO comment about figuring out if we can move this workaround - imre
v3:
* Rename cnp_irq_post_reset() to cnp_display_clock_wa()
* Add TODO item mentioning we need to clarify which platforms this
  workaround applies to
* Just use ibx_irq_reset() in gen8_irq_reset(). This code should be
  functionally equivalent on gen9 bc to the code v2 added
* Drop icp_hpd_irq_setup() call in spt_hpd_irq_setup(), this looks to be
  more or less identical to spt_hpd_irq_setup() minus additionally enabling
  one port. Will update i915 to use icp_hpd_irq_setup() for ICP in a
  separate patch.
v4:
* Revert Wa_14010685332 system list in comments to how it was before
* Add back HAS_PCH_SPLIT() check before calling ibx_irq_reset()

Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Tejas Upadhyay <tejaskumarx.surendrakumar.upadhyay@intel.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210217180016.1937401-1-lyude@redhat.com