net: do not take an additional reference in skb_frag_set_page

net: do not take an additional reference in skb_frag_set_page

I audited all of the callers in the tree and only one of them (pktgen) expects
it to do so. Taking this reference is pretty obviously confusing and error
prone.

In particular I looked at the following commits which switched callers of
(__)skb_frag_set_page to the skb paged fragment api:

8553876ae2f29cfc818ce2bbf935515d654f43c5 cxgb3: convert to SKB paged frag API.
5c53baf0bf02c2e2ee8356b887badd797307a6ac myri10ge: convert to SKB paged frag API.
32bd1e4808c472fc42b10efcb8039d508941a6d0 vmxnet3: convert to SKB paged frag API.
cb25246b91f0f57edba9271bad686aba544231e7 virtionet: convert to SKB paged frag API.
4599744db344048cc2bc7400e05f64911d3fddef sfc: convert to SKB paged frag API.
cf2aec86d8cd8fc2cd5a7aa893c9680110372b56 cassini: convert to SKB paged frag API.
ac32ff5d3c0436e466dd68e306a074155677cd76 benet: convert to SKB paged frag API.
da4c7e143c926b4860e54ae4f6433e953f93979a bnx2: convert to SKB paged frag API.
cd6819958156ff20b8a9090ff687c27f5b56ad33 net: xfrm: convert to SKB frag APIs
421924a26967d918a4eb4e9b631e46bdc51705a7 net: convert core to skb paged frag APIs

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>