drm/i915/display: Only write to register in intel_psr2_program_trans_man_trk_ctl()

drm/i915/display: Only write to register in intel_psr2_program_trans_man_trk_ctl()

There is no support for two pipes one transcoder for PSR and if we had
that the current code should not use cpu_transcoder.
Also I can't see a scenario where crtc_state->enable_psr2_sel_fetch is
set and PSR is not enabled and if by a bug it happens PSR HW will just
ignore any value in set in PSR2_MAN_TRK_CTL.

So dropping all the rest and keeping the same behavior that we have
with intel_psr2_program_plane_sel_fetch().

Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210209181439.215104-2-jose.souza@intel.com