drm/i915/dpio: Extract vlv_dpio_phy_regs.h

Pull the VLV/CHV DPIO PHY sideband registers to their own file.

v2: drop stray tabs (Jani)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240422083457.23815-15-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>