kconfig: Fix realloc usage()

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index dc5dcf2..c0efe10 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -878,7 +878,7 @@
 		newlen = strlen(res) + strlen(symval) + strlen(src);
 		if (newlen > reslen) {
 			reslen = newlen;
-			realloc(res, reslen);
+			res = realloc(res, reslen);
 		}
 
 		strcat(res, symval);