staging: erofs: update Kconfig

Keep in line with erofs-outofstaging patchset:
 - turn on CONFIG_EROFS_FS_ZIP by default;
 - turn on CONFIG_EROFS_FS_SECURITY by default suggested by David;
 - update Kconfig description.

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190731155752.210602-23-gaoxiang25@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>