mlx5en: Use a UMA cache zone for managing TLS send tags

Instead of allocating directly from a normal zone. This way
import and release are guaranteed to process all allocated and then
deallocated items. Also, the release occurs in a sleepable context when
caller of uma_zfree() or uma_zdestroy() can sleep itself.

Sponsored by: NVIDIA Networking

(cherry picked from commit 0f7b6e11c01d5360c9423d6938b160fe2d030ab0)