net: Rephrased comments section of skb_mpls_pop()

Rephrased comments section of skb_mpls_pop() to align it with
comments section of skb_mpls_push().

Signed-off-by: Martin Varghese <martin.varghese@nokia.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/skbuff.c

@@ -5533,7 +5533,7 @@ EXPORT_SYMBOL_GPL(skb_mpls_push);
  * @skb: buffer
  * @next_proto: ethertype of header after popped MPLS header
  * @mac_len: length of the MAC header
- * @ethernet: flag to indicate if ethernet header is present in packet
+ * @ethernet: flag to indicate if the packet is ethernet
  *
  * Expects skb->data at mac header.
  *