igb: skip phy status check where unavailable

igb_read_phy_reg() will silently return, leaving phy_data untouched, if
hw->ops.read_reg isn't set. Depending on the uninitialized value of
phy_data, this led to the phy status check either succeeding immediately
or looping continuously for 2 seconds before emitting a noisy err-level
timeout. This message went out to the console even though there was no
actual problem.

Instead, first check if there is read_reg function pointer. If not,
proceed without trying to check the phy status register.

Fixes: b72f3f72005d ("igb: When GbE link up, wait for Remote receiver status condition")
Signed-off-by: Kevin Mitchell <[e-mail]>
Tested-by: Gurucharan <[e-mail]> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/intel/igb/igb_main.c

···
 				break;
 			}
 
-			if (adapter->link_speed != SPEED_1000)
+			if (adapter->link_speed != SPEED_1000 ||
+			    !hw->phy.ops.read_reg)
 				goto no_wait;
 
 			/* wait for Remote receiver status OK */