init/modpost: conditionally check section mismatch to __meminit*

This reverts commit eb8f6890 ("Use separate sections for __dev/
_cpu/__mem code/data").

Check section mismatch to __meminit* only when CONFIG_MEMORY_HOTPLUG=n.

With this change, the linker script and modpost become simpler, and we
can get rid of the __ref annotations from the memory hotplug code.

[sfr@canb.auug.org.au: remove MEM_KEEP from arch/powerpc/kernel/vmlinux.lds.S]
  Link: https://lkml.kernel.org/r/20240710093213.2aefb25f@canb.auug.org.au
Link: https://lkml.kernel.org/r/20240706160511.2331061-2-masahiroy@kernel.org


Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>