linux-user: respect timezone for settimeofday

linux-user: respect timezone for settimeofday

The settimeofday syscall accepts a tz argument indicating the desired
timezone to the kernel. QEMU previously ignored any argument provided
by the target program & always passed NULL to the kernel. Instead,
translate the argument & pass along the data userland provided.

Although this argument is described by the settimeofday man page as
obsolete, it is used by systemd as of version 213.

Signed-off-by: Paul Burton <paul@archlinuxmips.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>