drm/i915/tv: split out TV regs to a separate file

Clean up i915_reg.h by splitting out TV regs to display/intel_tv_regs.h.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/be4a946a7772f5b4483ad9e078cb62158849683e.1678973282.git.jani.nikula@intel.com