drm/i915: Do not put big intel_crtc_state on the stack

Having this on stack triggers the -Wframe-larger-than=1024 and
is not nice to put such big things on the kernel stack anyway.

This required a little bit of refactoring to handle the new
failure path from vlv_force_pll_on.

v2: Corrected some whitespace.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: John Harrison <john.c.harrison@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1453217117-26125-1-git-send-email-tvrtko.ursulin@linux.intel.com