arch: types.h: factor out fixed width typedefs to int-ll64.h

All architectures have the same definition for s8/16/32/64
and u8/16/32/64.

Factor out the duplicated code into <asm-generic/int-ll64.h>.

BTW, Linux unified the kernel space definition into int-ll64.h
a few years ago as you see in Linux commit 0c79a8e29b5f
("asm/types.h: Remove include/asm-generic/int-l64.h").

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