crypto-arc4 move into a module with commitc3a78955f3, fs-nfs-common-rpcsec compile error without arc4 support. Ref: https://github.com/openwrt/packages/issues/9912 Fixes:c3a78955f3("kernel: move crypto-arc4 into a module") Signed-off-by: Ruixi Zhou <zhouruixi@gmail.com>