drm/i915: Don't switch to TPS1 when disabling DP_TP_CTL

drm/i915: Don't switch to TPS1 when disabling DP_TP_CTL

AFAICS Bspec has never asked us to switch to TPS1 when *disabling*
DP_TP_CTL. Let's stop doing that in case it confuses something.
We do have to switch before we *enable* DP_TP_CTL, but that
is already being handled correctly.

v2: Do the same for FDI
v3: Rebase

Reviewed-by: Imre Deak <imre.deak@intel.com> #v1
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230308212627.7601-1-ville.syrjala@linux.intel.com