drm/i915: Rename intel_shared_dpll_config to intel_shared_dpll_state

Struct intel_shared_dpll_config is used to hold the state of the DPLL in
the "atomic" sense, so call it state like everything else atomic.

v2: Rebase
Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v1)
Link: http://patchwork.freedesktop.org/patch/msgid/1483024933-3726-4-git-send-email-ander.conselvan.de.oliveira@intel.com