Enable CIFS/SMB kernel support in arm64 config (#681)

## Summary

Enables CIFS (SMB) filesystem support in the arm64 kernel config,
required for the SMB volume driver added in apple/container#1414.

Without this change, SMB mounts fail at runtime with `errno 19
(ENODEV)`.

## Changes

- `kernel/config-arm64`: enable `CONFIG_CIFS=y` and related options
(`CIFS_ALLOW_INSECURE_LEGACY`, `CIFS_UPCALL`, `CIFS_XATTR`,
`CIFS_POSIX`, `CIFS_DFS_UPCALL`)

Author: tonycoco

kernel/config-arm64

@@ -3503,7 +3503,15 @@ CONFIG_RPCSEC_GSS_KRB5=y
 # CONFIG_SUNRPC_DISABLE_INSECURE_ENCTYPES is not set
 # CONFIG_SUNRPC_DEBUG is not set
 # CONFIG_CEPH_FS is not set
-# CONFIG_CIFS is not set
+CONFIG_CIFS=y
+# CONFIG_CIFS_STATS2 is not set
+CONFIG_CIFS_ALLOW_INSECURE_LEGACY=y
+CONFIG_CIFS_UPCALL=y
+CONFIG_CIFS_XATTR=y
+CONFIG_CIFS_POSIX=y
+# CONFIG_CIFS_DEBUG is not set
+CONFIG_CIFS_DFS_UPCALL=y
+# CONFIG_CIFS_SMB_DIRECT is not set
 # CONFIG_SMB_SERVER is not set
 # CONFIG_CODA_FS is not set
 # CONFIG_AFS_FS is not set