Without this, a bo may get created in the cpu-inaccessible vram.
Before the CP engines get setup, all copies are done via cpu memcpy.

This means that the cpu tries to read from inaccessible memory, fails,
and the radeon module proceeds to disable acceleration.

Doing this has no downsides, as the real VRAM size gets set as soon as the
CP engines get init.

This is a candidate for 3.14 fixes.

v2: Add comment on why the function is used
Signed-off-by: Lauri Kasanen <cand@gmx.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Cc: stable@vger.kernel.org