nfs-kernel-server: disable kerberos and ldap

nfs-kernel-server: disable kerberos and ldap

Some targets are failing due likely to build order issues suggested by
Daniel[1] so disable these two options for the v4 package.

Example:
make[4]: Leaving directory '/builder/shared-workdir/build/sdk/build_dir/target-aarch64_cortex-a53_musl/nfs-utils-2.8.4'
Package nfs-kernel-server-v4 is missing dependencies for the following libraries:
libgssapi_krb5.so.2
libldap.so.2

1. https://github.com/openwrt/packages/pull/27150#issuecomment-3446589119

Signed-off-by: John Audia <[email protected]>