NFSD: Move "select NFSD_V2_ACL if NFSD_V3_ACL"

Clean up: since NFSD_V2_ACL is a boolean, it can be selected safely
under the NFSD_V3_ACL entry (also a boolean).

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>