nbd: fix download URL

The old URL nowadays return a 404.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/nbd/nbd.mk

@@ -6,7 +6,7 @@
 
 NBD_VERSION = 3.0
 NBD_SOURCE = nbd-$(NBD_VERSION).tar.bz2
-NBD_SITE = http://$(BR2_SOURCEFORGE_MIRROR).dl.sourceforge.net/sourceforge/nbd/
+NBD_SITE = http://$(BR2_SOURCEFORGE_MIRROR).dl.sourceforge.net/project/nbd/nbd/$(NBD_VERSION)
 NBD_CONF_OPT = $(if $(BR2_LARGEFILE),--enable-lfs,--disable-lfs)
 NBD_DEPENDENCIES = libglib2