dma-buf: Suppress a thread-safety complaint

dma-buf: Suppress a thread-safety complaint

Handle all possible dma_resv_lock() return values. This patch prepares
for enabling compile-time thread-safety analysis. This will cause the
compiler to check whether all dma_resv_lock() return values are handled.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20260227165501.2062829-1-bvanassche@acm.org