drm/i915/tgl: rename TRANSCODER_EDP_VDSC to use on transcoder A

drm/i915/tgl: rename TRANSCODER_EDP_VDSC to use on transcoder A

On TGL the special EDP transcoder is gone and it should be handled by
transcoder A.

v2 (Lucas):
  - Reuse POWER_DOMAIN_TRANSCODER_EDP_VDSC (suggested by Ville)
  - Use crtc->dev since new_crtc_state->state may be NULL on atomic
    commit (suggested by Maarten)
v3 (Lucas):
  - Rename power domain so it's clear it can also be used for transcoder
    A in TGL (requested by José and Manasi)

Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Acked-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190711173115.28296-8-lucas.demarchi@intel.com