[CIFS] quiet sparse compile warning

Jeff's patchset introduced trivial sparse warning on new cifs toupper routine
Signed-off-by: Steve French <smfrench@gmail.com>
CC: Jeff Layton <jlayton@redhat.com>

fs/cifs/winucase.c

@@ -31,6 +31,8 @@
 
 #include <linux/nls.h>
 
+wchar_t cifs_toupper(wchar_t in);  /* quiet sparse */
+
 static const wchar_t t2_00[256] = {
 	0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
 	0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,