Revert "drm/ttm: Warn on pinning without holding a reference"

Revert "drm/ttm: Warn on pinning without holding a reference"

BugLink: https://bugs.launchpad.net/bugs/1922600
This reverts commit 7d09e9725b5dcc8d14e101de931e4969d033a6ad which is
commit 57fcd550eb15bce14a7154736379dfd4ed60ae81 upstream.

It is causing too many warnings on 5.11.y, so should be dropped for now.

Cc: Huang Rui <ray.huang@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Christian Koenig <christian.koenig@amd.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Sasha Levin <sashal@kernel.org>
Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Link: https://lore.kernel.org/r/8c3da8bc-0bf3-496f-1fd6-4f65a07b2d13@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>