drm/fb-helper: Fix fb refcounting in pan_display_atomic

drm/fb-helper: Fix fb refcounting in pan_display_atomic

In

commit 73f1c2c78fb230afa0ec4aa2b1c908b6ed4a76ac
Author: Rob Clark <robdclark@gmail.com>
Date:   Tue Aug 25 15:35:58 2015 -0400

    drm/fb-helper: atomic restore_fbdev_mode()..

we've forgotten to do the plane->old_fb refcount dance for
pan_display_atomic, which can result in refcount leaks if the current
configuration is not from fbcon. Which apparently can happen when
vt-switching - fbcon does a pan first before a set_par.

OCD-align function parameters while at it.

v2: Actually git add the OCD.

Cc: Rob Clark <robdclark@gmail.com>
Cc: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92483
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1445015490-27682-1-git-send-email-daniel.vetter@ffwll.ch
Tested-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>