vmwgfx: Optimize the command submission resource list

Use a list for resources referenced during command submission, instead of
an array.
As long as we don't implement parallell command submission this works fine
and simplifies things a bit.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>