Fix the compiler warning when cross build qemu-ga
for windows by using qemu_setsockopt() instead of
setsockopt().

util/osdep.c: In function 'socket_set_nodelay':
util/osdep.c:69:5: warning: passing argument 4 of 'setsockopt' from
                   incompatible pointer type [enabled by default]
In file included from /home/lei/qemu_b/include/sysemu/os-win32.h:30:0,
                 from /home/lei/qemu_b/include/qemu-common.h:46,
                 from util/osdep.c:48:
/usr/i686-w64-mingw32/sys-root/mingw/include/winsock2.h:990:63: note:
                 expected 'const char *' but argument is of type 'int *'

Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>