memcg: manually uninline __memcg_memory_event

memcg: manually uninline __memcg_memory_event

__memcg_memory_event() has been unnecessarily marked inline even when it
is not really performance critical.  It is usually called to track extreme
conditions.  Over the time, it has evolved to include more functionality
and inlining it is causing more harm.

Before the patch:
$ size mm/memcontrol.o net/ipv4/tcp_input.o net/ipv4/tcp_output.o
   text    data     bss     dec     hex filename
  35645   10574    4192   50411    c4eb mm/memcontrol.o
  54738    1658       0   56396    dc4c net/ipv4/tcp_input.o
  34644    1065       0   35709    8b7d net/ipv4/tcp_output.o

After the patch:
$ size mm/memcontrol.o net/ipv4/tcp_input.o net/ipv4/tcp_output.o
   text    data     bss     dec     hex filename
  35137   10446    4192   49775    c26f mm/memcontrol.o
  54322    1562       0   55884    da4c net/ipv4/tcp_input.o
  34492    1017       0   35509    8ab5 net/ipv4/tcp_output.o

[akpm@linux-foundation.org: use EXPORT_SYMBOL_GPL for __memcg_memory_event, per Michal and Christoph]
Link: https://lkml.kernel.org/r/20251021234425.1885471-1-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: SeongJae Park <sj@kernel.org>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>