The separation between GEM VRAM objects and the memory manager is
artificial, as they are only used with each other. Copying both
implementations into the same file is a first step to simplifying
the code.

This patch only moves code without functional changes.

v3:
	* update to use dev->vma_offset_manager
v2:
	* update for debugfs support
	* typos in commit message
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190911110910.30698-2-tzimmermann@suse.de