Fix an issue where dump stack is printed on suspend resume flow due to
netif_set_real_num_rx_queues() is not called with rtnl_lock held().

Fixes: 686cff3d ("net: stmmac: Fix incorrect location to set real_num_rx|tx_queues")
Reported-by: NChristophe ROULLIER <christophe.roullier@st.com>
Tested-by: NChristophe ROULLIER <christophe.roullier@st.com>
Cc: Alexandre TORGUE <alexandre.torgue@st.com>
Reviewed-by: NOng Boon Leong <boon.leong.ong@intel.com>
Signed-off-by: NWong Vee Khee <vee.khee.wong@intel.com>
Link: https://lore.kernel.org/r/20201115074210.23605-1-vee.khee.wong@intel.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>