tools arch uapi: Copy missing unistd.h headers for arc, hexagon and riscv

tools arch uapi: Copy missing unistd.h headers for arc, hexagon and riscv

Since those were introduced in:

  36be8269480d ("asm-generic: Make time32 syscall numbers optional")

But when the asm-generic/unistd.h was sync'ed with tools/ in:

  8e27d8c62baf ("tools headers uapi: Sync copy of asm-generic/unistd.h with the kernel sources")

I forgot to copy the files for the architectures that define
__ARCH_WANT_TIME32_SYSCALLS, so the perf build was breaking there, as
reported by Vineet Gupta for the ARC architecture.

After updating my ARC container to use the glibc based toolchain + cross
building libnuma, zlib and elfutils, I finally managed to reproduce the
problem and verify that this now is fixed and will not regress as will
be tested before each pull req sent upstream.

Reported-by: Vineet Gupta <Vineet.Gupta1@synopsys.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Jiri Olsa <jolsa@kernel.org>
CC: linux-snps-arc@lists.infradead.org
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/r/20190426193531.GC28586@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>