drm/i915: Do intel_dpll_readout_hw_state() after encoder readout

drm/i915: Do intel_dpll_readout_hw_state() after encoder readout

The clock readout for DDI encoders needs to moved into the encoders.
To that end intel_dpll_readout_hw_state() needs to happen after
the encoder readout as otherwise it can't correctly populate
the PLL crtc_mask/active_mask bitmasks.

v2: Populate DPLL ref clocks before the encoder->get_config()

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210225161225.30746-1-ville.syrjala@linux.intel.com
Reviewed-by: Mika Kahola <mika.kahola@intel.com>