igb: Fix reg pattern test in ethtool for i350 devices

This fixes the reg_pattern_test so that the test does not fail
on i350 parts.

Signed-off-by: Carolyn Wyborny <carolyn.wyborny@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/igb/igb_ethtool.c

@@ -1070,7 +1070,7 @@ static bool reg_pattern_test(struct igb_adapter *adapter, u64 *data,
 		{0x5A5A5A5A, 0xA5A5A5A5, 0x00000000, 0xFFFFFFFF};
 	for (pat = 0; pat < ARRAY_SIZE(_test); pat++) {
 		wr32(reg, (_test[pat] & write));
-		val = rd32(reg);
+		val = rd32(reg) & mask;
 		if (val != (_test[pat] & write & mask)) {
 			dev_err(&adapter->pdev->dev, "pattern test reg %04X "
 				"failed: got 0x%08X expected 0x%08X\n",