collectd: uses fork(), so mark it as mmu only

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

package/collectd/Config.in

@@ -1,5 +1,7 @@
 config BR2_PACKAGE_COLLECTD
 	bool "collectd"
+	# Uses fork()
+	depends on BR2_USE_MMU
 	depends on BR2_TOOLCHAIN_HAS_THREADS
 	help
 	  collectd is a daemon which collects system performance