config: Fix ngx_module_type

Since commit 37182ce2f3 the module was not present in static builds
because due to an invalid "ngx_module_type" the module was not added to
objs/ngx_modules.c.

This commit will fix the problem by setting the correct module type
"HTTP_FILTER" [Link 1].

Link 1: https://www.nginx.com/resources/wiki/extending/new_config/#key-ngx_module_type
Gentoo-Bug: https://bugs.gentoo.org/593450
Fixes: https://github.com/masterzen/nginx-upload-progress-module/issues/50

config

@@ -1,6 +1,6 @@
 ngx_addon_name=ngx_http_uploadprogress_module
 if test -n "$ngx_module_link"; then
-    ngx_module_type=FILTER
+    ngx_module_type=HTTP_FILTER
     ngx_module_name=ngx_http_uploadprogress_module
     ngx_module_srcs="$ngx_addon_dir/ngx_http_uploadprogress_module.c"