net/mlx5e: fix TLS dependency

With CONFIG_TLS=m and MLX5_CORE_EN=y, we get a link failure:

drivers/net/ethernet/mellanox/mlx5/core/en_accel/tls_rxtx.o: In function `mlx5e_tls_handle_ooo':
tls_rxtx.c:(.text+0x24c): undefined reference to `tls_get_record'
drivers/net/ethernet/mellanox/mlx5/core/en_accel/tls_rxtx.o: In function `mlx5e_tls_handle_tx_skb':
tls_rxtx.c:(.text+0x9a8): undefined reference to `tls_device_sk_destruct'

This narrows down the dependency to only allow the configurations
that will actually work. The existing dependency on TLS_DEVICE is
not sufficient here since MLX5_EN_TLS is a 'bool' symbol.

Fixes: c83294b9

 ("net/mlx5e: TLS, Add Innova TLS TX support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Saeed Mahameed <saeedm@mellanox.com>
Acked-by: Boris Pismenny <borisp@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>