dropbear: fix initscript install

The -D option to install only works portably when the destination is
a file. Specifying the filename avoids the following build error (at
least on some hosts):

"/usr/bin/install: cannot overwrite directory `/tmp/buildroot/
project_build_foobar/uclibc/root/etc/init.d' with non-directory"

Signed-off-by: Marc Gauthier <marc@tensilica.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/dropbear/dropbear.mk

@@ -28,7 +28,7 @@ $(DROPBEAR_TARGET_INSTALL_TARGET):
 	ln -snf ../sbin/dropbear $(TARGET_DIR)/usr/bin/scp
 	ln -snf ../sbin/dropbear $(TARGET_DIR)/usr/bin/ssh
 	if [ ! -f $(TARGET_DIR)/etc/init.d/S50dropbear ]; then \
-		$(INSTALL) -m 0755 -D package/dropbear/S50dropbear $(TARGET_DIR)/etc/init.d; \
+		$(INSTALL) -m 0755 -D package/dropbear/S50dropbear $(TARGET_DIR)/etc/init.d/S50dropbear; \
 	fi
 	touch $@