drm/i915: Use global atomic state for staged pll, config, v3.

drm/i915: Use global atomic state for staged pll, config, v3.

Now that we can subclass drm_atomic_state we can also use it to keep
track of all the pll settings. atomic_state is a better place to hold
all shared state than keeping pll->new_config everywhere.

Changes since v1:
- Assert connection_mutex is held.
Changes since v2:
- Fix swapped arguments to kzalloc for intel_atomic_state_alloc. (Jani Nikula)

Signed-off-by: Ander Conselvan de Oliveira <[email protected]>
Signed-off-by: Maarten Lankhorst <[email protected]>
Reviewed-by: Matt Roper <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>