stmmac: Remove spin_lock call in stmmac_get_pauseparam()

The following patch removed unnecessary spin_lock/unlock calls
in ethtool_ops callback functions. In the second and final version
of the patch one spin_lock call was left behind.

commit cab6715c
Author: Yang Wei <Wei.Yang@windriver.com>
Date:   Sun May 25 09:53:44 2014 +0800

    net: driver: stmicro: Remove some useless the lock protection

This introduced the following sparse warning:

drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c:424:1: warning:
	context imbalance in 'stmmac_get_pauseparam' -
	different lock contexts for basic block

Signed-off-by: Emil Goode <emilgoode@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>