igc: change default return of igc_read_phy_reg()

stable inclusion
from stable-5.10.54
commit 02d1af0bee65d8746f5630b648a8778ff57b5a70
bugzilla: 175586 https://gitee.com/openeuler/kernel/issues/I4DVDU

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=02d1af0bee65d8746f5630b648a8778ff57b5a70

--------------------------------

[ Upstream commit 05682a0a ]

Static analysis reports this problem

igc_main.c:4944:20: warning: The left operand of '&'
  is a garbage value
    if (!(phy_data & SR_1000T_REMOTE_RX_STATUS) &&
          ~~~~~~~~ ^

phy_data is set by the call to igc_read_phy_reg() only if
there is a read_reg() op, else it is unset and a 0 is
returned.  Change the return to -EOPNOTSUPP.

Fixes: 208983f0 ("igc: Add watchdog")
Signed-off-by: NTom Rix <trix@redhat.com>
Tested-by: NDvora Fuxbrumer <dvorax.fuxbrumer@linux.intel.com>
Signed-off-by: NTony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/net/ethernet/intel/igc/igc.h

@@ -532,7 +532,7 @@ static inline s32 igc_read_phy_reg(struct igc_hw *hw, u32 offset, u16 *data)
 	if (hw->phy.ops.read_reg)
 		return hw->phy.ops.read_reg(hw, offset, data);
 
-	return 0;
+	return -EOPNOTSUPP;
 }
 
 void igc_reinit_locked(struct igc_adapter *);