The registers and process differ from other platforms. If the hardware
was programmed incorrectly, this will return invalid cdclk values, which
should then cause reprogramming of the hardware.

v2(Matt): Return 19.2 MHz when DE PLL is disabled (Ville)
v3: Make less assumptions about the hardware state (Ville)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Bob Paauwe <bob.j.paauwe@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>