memcg: cleanup __mod_memcg_lruvec_state

There are no memcg specific stats for NR_SHMEM_PMDMAPPED and
NR_FILE_PMDMAPPED.  Let's remove them.

Link: https://lkml.kernel.org/r/20240501172617.678560-6-shakeel.butt@linux.dev


Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: T.J. Mercier <tjmercier@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>