drm/i915: Drop redundant !modeset check

Since commit 7de5b6b5 ("drm/i915: Don't flag both full
modeset and fastset at the same time")
intel_crtc_needs_fastset() and intel_crtc_needs_modeset() have
been mutually exclusive. Drop the redundant check.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230907122541.32261-2-ville.syrjala@linux.intel.com


Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>