http: resolve dead code warning for mod_fastcgi_push_params_end

CID 1590465: (#1 of 1): Logically dead code (DEADCODE)
dead_error_line: Execution cannot reach this statement:
	return pack_result::failure;.

Fixes: gromox-0~666

Author: jengelh

exch/http/fastcgi.cpp

@@ -298,7 +298,7 @@ static pack_result mod_fastcgi_push_params_end(NDR_PUSH *pndr)
 
 	offset = pndr->offset;
 	len = offset - 8;
-	if (len > 0xFFFF)
+	if (offset > 0xFFFF)
 		return pack_result::failure;
 	pndr->offset = 4;
 	TRY(pndr->p_uint16(len));