crypto-arc4 move into a module with commit c3a78955f3,
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>
b30e481b6c