busybox: enable flock applet

Needed by E.G. the default odhcp6c state script.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/busybox/busybox.config

@@ -575,7 +575,7 @@ CONFIG_FEATURE_FDISK_WRITABLE=y
 CONFIG_FEATURE_GPT_LABEL=y
 CONFIG_FEATURE_FDISK_ADVANCED=y
 # CONFIG_FINDFS is not set
-# CONFIG_FLOCK is not set
+CONFIG_FLOCK=y
 CONFIG_FREERAMDISK=y
 # CONFIG_FSCK_MINIX is not set
 # CONFIG_MKFS_EXT2 is not set