drm/i915: Introduce struct intel_vblank_evade_ctx

drm/i915: Introduce struct intel_vblank_evade_ctx

Collect the information needed for vblank evasions into
a structure that we can pass around more easily.

And let's rename intel_crtc_vblank_evade_scanlines() to just
intel_vblank_evade_init() so that better describes the intended
usage of initializing the context.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231213102519.13500-4-ville.syrjala@linux.intel.com
Reviewed-by: Uma Shankar <uma.shankar@intel.com>