linux-user: Fix setreuid and setregid to use direct syscalls

linux-user: Fix setreuid and setregid to use direct syscalls

The commit fd6f7798ac30 ("linux-user: Use direct syscalls for setuid(),
etc") added direct syscall wrappers for setuid(), setgid(), etc since the
system calls have different semantics than the libc functions.

Add and use the corresponding wrappers for setreuid and setregid which
were missed in that commit.

This fixes the build of the debian package of the uid_wrapper library
(https://cwrap.org/uid_wrapper.html) when running linux-user.

Cc: qemu-stable@nongnu.org
Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-ID: <Zyo2jMKqq8hG8Pkz@p100>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
(cherry picked from commit 8491026a08b417b2d4070f7c373dcb43134c5312)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>