SPDY: fixed build, broken by b7ee1bae0ffa.

False positive warning about the "cl" variable may be uninitialized in
the ngx_http_spdy_filter_get_data_frame() call was suppressed.

It is always initialized either in the "while" cycle or in the following
"if" condition since frame_size cannot be zero.

src/http/ngx_http_spdy_filter_module.c

diff --git a/src/http/ngx_http_spdy_filter_module.c b/src/http/ngx_http_spdy_filter_module.c
index 2bf3485..5d45ebc 100644
--- a/src/http/ngx_http_spdy_filter_module.c
+++ b/src/http/ngx_http_spdy_filter_module.c
@@ -665,6 +665,10 @@
         offset = 0;
     }
 
+#if (NGX_SUPPRESS_WARN)
+    cl = NULL;
+#endif
+
     slcf = ngx_http_get_module_loc_conf(r, ngx_http_spdy_module);
 
     frame_size = (limit && limit <= (off_t) slcf->chunk_size)