net: stmmac: add mutex lock to protect est parameters

[ Upstream commit b2aae654 ]

Add a mutex lock to protect est structure parameters so that the
EST parameters can be updated by other threads.

Signed-off-by: Xiaoliang Yang <xiaoliang.yang_1@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Pavel Machek (CIP) <pavel@denx.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>