init: remove unused __MEMINIT* macros

These macros are not used anywhere.

Link: https://lkml.kernel.org/r/20240706160511.2331061-1-masahiroy@kernel.org


Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>