drm/i915/display: Include i915_active header in frontbuffer tracking code

Intel frontbuffer tracking code is using i915_active functions -> include
i915_active.h directly instead of relying getting indirectly included.

Cc: Jani Nikula <jani.nikula@intel.com>

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230929112047.1151914-1-jouni.hogander@intel.com