semaphore: consolidate arch headers into a generic one

This consolidates the copy-pasted arch specific semaphore header into
single version (based on s390) which suffices 32-bit and and 64-bit
arch/ABI based on the canonical WORDSIZE.

For now I've left out arches which use alternate defines to choose for
32 vs 64-bit builds (aarch64, mips) which in theory can also use the same
header.

Passes build-many for
  aarch64-linux-gnu arm-linux-gnueabi arm-linux-gnueabihf
  riscv64-linux-gnu-rv64imac-lp64 riscv64-linux-gnu-rv64imafdc-lp64
  x86_64-linux-gnu microblaze-linux-gnu nios2-linux-gnu

Suggested-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>