util/romcc: Fix resource leak

Change-Id: I0d260254bab714ec939fc199b3a133b0fc05b10d
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Found-by: Coverity Scan #1129112
Reviewed-on: https://review.coreboot.org/17883
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

util/romcc/romcc.c

@@ -10779,6 +10779,7 @@ static struct triple *string_constant(struct compile_state *state)
 		ptr = buf;
 		buf = xmalloc(type->elements + str_len + 1, "string_constant");
 		memcpy(buf, ptr, type->elements);
+		free(ptr);
 		ptr = buf + type->elements;
 		do {
 			*ptr++ = char_value(state, &str, end);