drm/atomic-helper: Change parameter name of drm_atomic_helper_wait_for_vblanks()

drm/atomic-helper: Change parameter name of drm_atomic_helper_wait_for_vblanks()

drm_atomic_helper_wait_for_vblanks() waits for vblank events on all the
CRTCs affected by a commit. It takes the drm_atomic_state being
committed as a parameter.

However, that parameter name is called (and documented) as old_state,
which is pretty confusing. Let's rename that variable as state.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20250213-bridge-connector-v3-23-e71598f49c8f@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>