net: always inline skb_frag_unref() and __skb_frag_unref()

net: always inline skb_frag_unref() and __skb_frag_unref()

clang is not inlining skb_frag_unref() and __skb_frag_unref()
in gro fast path.

It also does not inline gro_try_pull_from_frag0().

Using __always_inline fixes this issue, makes the
kernel faster _and_ smaller.

Also change __skb_frag_ref(), skb_frag_ref() and skb_page_unref()
to let them inlined for the last patch in this series.

$ scripts/bloat-o-meter -t vmlinux.0 vmlinux.1
add/remove: 2/6 grow/shrink: 1/2 up/down: 218/-511 (-293)
Function                                     old     new   delta
gro_pull_from_frag0                            -     188    +188
__pfx_gro_pull_from_frag0                      -      16     +16
skb_shift                                   1125    1139     +14
__pfx_skb_frag_unref                          16       -     -16
__pfx_gro_try_pull_from_frag0                 16       -     -16
__pfx___skb_frag_unref                        16       -     -16
__skb_frag_unref                              36       -     -36
skb_frag_unref                                59       -     -59
dev_gro_receive                             1608    1514     -94
napi_gro_frags                               892     771    -121
gro_try_pull_from_frag0                      153       -    -153
Total: Before=22566192, After=22565899, chg -0.00%

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260122045720.1221017-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>