drm/i915/display: Add intel_fb_bo_framebuffer_fini

Xe needs intel_fb_bo_framebuffer_fini for taking care of unpinning the fb
and taking reference.  In i915 this can be empty.

Also move intel_frontbuffer_get to be done after
intel_fb_bo_framebuffer_init to have reasonable sequences:

intel_fb_bo_framebuffer_init
intel_frontbuffer_get
...
intel_frontbuffer_put
intel_fb_bo_framebuffer_fini

v2: Empty function instead of define

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231207083451.2184562-1-jouni.hogander@intel.com