e1000e: test for valid check_reset_block function pointer

commit 44abd5c12767a8c567dc4e45fd9aec3b13ca85e0 introduced NULL pointer
dereferences when attempting to access the check_reset_block function
pointer on 8257x and 80003es2lan non-copper devices.

This fix should be applied back through 3.4.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index a4b0435..31d37a2 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -6237,7 +6237,7 @@
 		adapter->hw.phy.ms_type = e1000_ms_hw_default;
 	}
 
-	if (hw->phy.ops.check_reset_block(hw))
+	if (hw->phy.ops.check_reset_block && hw->phy.ops.check_reset_block(hw))
 		e_info("PHY reset is blocked due to SOL/IDER session.\n");
 
 	/* Set initial default active device features */
@@ -6404,7 +6404,7 @@
 	if (!(adapter->flags & FLAG_HAS_AMT))
 		e1000e_release_hw_control(adapter);
 err_eeprom:
-	if (!hw->phy.ops.check_reset_block(hw))
+	if (hw->phy.ops.check_reset_block && !hw->phy.ops.check_reset_block(hw))
 		e1000_phy_hw_reset(&adapter->hw);
 err_hw_init:
 	kfree(adapter->tx_ring);