drm/i915: s/pipe_config/new_crtc_state/ in .crtc_enable()

Rename pipe_config to new_crtc_state in the .crtc_enable() hooks.
The 'pipe_config' name is a zombie that we need to finally put down.
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191118164430.27265-10-ville.syrjala@linux.intel.com