net/mlx5e: Return in default case statement in tx_post_resync_params

clang warns:

drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c:251:2:
warning: variable 'rec_seq_sz' is used uninitialized whenever switch
default is taken [-Wsometimes-uninitialized]
default:
^~~~~~~
drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c:255:46: note:
uninitialized use occurs here
skip_static_post = !memcmp(rec_seq, &rn_be, rec_seq_sz);
^~~~~~~~~~
drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c:239:16: note:
initialize the variable 'rec_seq_sz' to silence this warning
u16 rec_seq_sz;
^
= 0
1 warning generated.

This case statement was clearly designed to be one that should not be
hit during runtime because of the WARN_ON statement so just return early
to prevent copying uninitialized memory up into rn_be.

Fixes: d2ead1f360e8 ("net/mlx5e: Add kTLS TX HW offload support")
Link: https://github.com/ClangBuiltLinux/linux/issues/590
Signed-off-by: Nathan Chancellor <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c

···
 	}
 	default:
 		WARN_ON(1);
+		return;
 	}
 
 	skip_static_post = !memcmp(rec_seq, &rn_be, rec_seq_sz);