idpf: only assign num refillqs if allocation was successful

As reported by AI review [1], if the refillqs allocation fails, refillqs
will be NULL but num_refillqs will be non-zero. The release function
will then dereference refillqs since it thinks the refillqs are present,
resulting in a NULL ptr dereference.

Only assign the num refillqs if the allocation was successful. This will
prevent the release function from entering the loop and accessing
refillqs.

[1] https://lore.kernel.org/netdev/20260227035625.2632753-1-kuba@kernel.org/

Fixes: 95af467d9a4e3 ("idpf: configure resources for RX queues")
Signed-off-by: Joshua Hay <joshua.a.hay@intel.com>
Reviewed-by: Madhu Chittim <madhu.chittim@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>