net/mlx5e: Allow concurrent creation of hairpin entries

Hairpin entries creation is fully synchronized by hairpin_tbl_lock. In
order to allow concurrent initialization of mlx5e_hairpin structure
instances and provisioning of hairpin entries to hardware, extend
mlx5e_hairpin_entry with 'res_ready' completion. Move call to
mlx5e_hairpin_create() out of hairpin_tbl_lock critical section. Modify
code that attaches new flows to existing hpe to wait for 'res_ready'
completion before using the hpe. Insert hpe to hairpin table before
provisioning it to hardware and modify all users of hairpin table to verify
that hpe was fully initialized by checking hpe->hp pointer (and to wait for
'res_ready' completion, if necessary).

Modify dead peer update event handling function to save hpe's to temporary
list with their reference counter incremented. Wait for completion of hpe's
in temporary list and update their 'peer_gone' flag outside of
hairpin_tbl_lock critical section.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>