drm/i915/lt_phy: Replace crtc compute clock

drm/i915/lt_phy: Replace crtc compute clock

The existing DPLL compute clock callback for the XE3PLPD platform
(`xe3plpd_crtc_compute_clock`) was specific to that platform. Replace it
with the more generic Haswell (`hsw_crtc_compute_clock`) implementation
so that the compute clock path does not rely on the XE3PLPD hook.

Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://patch.msgid.link/20260312080657.2648265-25-mika.kahola@intel.com