bpf: Remove __bpf_local_storage_map_alloc

bpf_local_storage_map_alloc() is the only caller of
__bpf_local_storage_map_alloc().  The remaining logic in
bpf_local_storage_map_alloc() is only a one liner setting
the smap->cache_idx.

Remove __bpf_local_storage_map_alloc() to simplify code.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20230308065936.1550103-4-martin.lau@linux.dev


Signed-off-by: Alexei Starovoitov <ast@kernel.org>