ixgbe: Resolve warnings for -Wimplicit-fallthrough

This patch adds/changes fall through comments to address new warnings
produced by gcc 7.

Fixed formatting on a couple of comments in the function.

Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
index 3af6127..76ad0e0 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
@@ -155,7 +155,7 @@ s32 ixgbe_setup_fc_generic(struct ixgbe_hw *hw)
 		if (ret_val)
 			return ret_val;
 
-		/* only backplane uses autoc so fall though */
+		/* fall through - only backplane uses autoc */
 	case ixgbe_media_type_fiber:
 		reg = IXGBE_READ_REG(hw, IXGBE_PCS1GANA);
 
@@ -3549,7 +3549,7 @@ void ixgbe_set_rxpba_generic(struct ixgbe_hw *hw,
 		rxpktsize <<= IXGBE_RXPBSIZE_SHIFT;
 		for (; i < (num_pb / 2); i++)
 			IXGBE_WRITE_REG(hw, IXGBE_RXPBSIZE(i), rxpktsize);
-		/* Fall through to configure remaining packet buffers */
+		/* fall through - configure remaining packet buffers */
 	case (PBA_STRATEGY_EQUAL):
 		/* Divide the remaining Rx packet buffer evenly among the TCs */
 		rxpktsize = (pbsize / (num_pb - i)) << IXGBE_RXPBSIZE_SHIFT;