h8300: move definition of __kernel_size_t etc. to posix_types.h

These types should be defined in posix_types.h, not in bitsperlong.h .

With these defines moved, h8300-specific bitsperlong.h is no longer
needed since Kbuild will automatically create a wrapper of
include/uapi/asm-generic/bitsperlong.h

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>