If allocating the DMA buffer fails, mana_hwc_destroy_wq was called
without previously storing the pointer to the queue.

In order to avoid leaking the pointer to the queue, store it as soon as
it is allocated.

Addresses-Coverity-ID: 1484720 ("Resource leak")
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Link: https://lore.kernel.org/r/20211208223723.18520-1-jose.exposito89@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>