Cygwin: Fix warnings about narrowing conversions of socket ioctls

Fix gcc 12 warnings about narrowing conversions of socket ioctl constants
when used as case labels, e.g:

> ../../../../src/winsup/cygwin/net.cc: In function ‘int get_ifconf(ifconf*, int)’:
> ../../../../src/winsup/cygwin/net.cc:1940:18: error: narrowing conversion of ‘2152756069’ from ‘long int’ to ‘int’ [-Wnarrowing]

Signed-off-by: Jon Turney <jon.turney@dronecode.org.uk>

winsup/cygwin/fhandler/socket.cc

@@ -86,7 +86,7 @@ struct __old_ifreq {
 int
 fhandler_socket::ioctl (unsigned int cmd, void *p)
 {
-  extern int get_ifconf (struct ifconf *ifc, int what); /* net.cc */
+  extern int get_ifconf (struct ifconf *ifc, unsigned int what); /* net.cc */
   int res;
   struct ifconf ifc, *ifcp;
   struct ifreq *ifrp;

winsup/cygwin/net.cc

@@ -1912,7 +1912,7 @@ freeifaddrs (struct ifaddrs *ifp)
 }
 
 int
-get_ifconf (struct ifconf *ifc, int what)
+get_ifconf (struct ifconf *ifc, unsigned int what)
 {
   __try
     {