drm: Extract add_hdmi_mode() out of do_hdmi_vsdb_modes()
drm: Extract add_hdmi_mode() out of do_hdmi_vsdb_modes()

So we respect a nice design of having similar functions at the same
level, in this case:

do_hdmi_vsdb_modes()
  - add_hdmi_mandatory_stereo_modes()
  - add_hdmi_mode()

Reviewed-by: Ville Syrjälä <cd6e8d405ca90be3a03d5427c5b24fbd2d68dcc4@linux.intel.com>
Signed-off-by: Damien Lespiau <64bd3cb94f359c1a3ce68dae5e26b40578526277@intel.com>
Acked-by: Dave Airlie <f2295d84e358395675bc8031be58672073ae065e@gmail.com>
Signed-off-by: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs