drm: Reserve/unreserve GEM VRAM BOs from within pin/unpin functions

drm: Reserve/unreserve GEM VRAM BOs from within pin/unpin functions

The original bochs and vbox implementations of pin and unpin functions
automatically reserved BOs during validation. This functionality got lost
while converting the code to a generic implementation. This may result
in validating unlocked TTM BOs.

Adding the reserve and unreserve operations to GEM VRAM's pin and unpin
functions fixes the bochs and vbox drivers. Additionally the patch changes
the mgag200, ast and hibmc drivers to not reserve BOs by themselves.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reported-by: kernel test robot <lkp@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20190516162746.11636-3-tzimmermann@suse.de
Fixes: a3232987fdbf ("drm/bochs: Convert bochs driver to |struct drm_gem_vram_object|")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>