drm/i915/xe2lpd: Add support for HPD

Hotplug setup for Xe2_LPD differs from Xe_LPD+ by the fact that the
extra programming for hotplug inversion and DDI HPD filter duration is
not necessary anymore. As mtp_hpd_irq_setup() is reasonably small,
prefer to fork it into a new function for Xe2_LPD instead of adding a
platform check.

v2: Add extra bspec reference and fix missing else (Matt Roper)

BSpec: 68970, 69940
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230919192128.2045154-16-lucas.demarchi@intel.com