nfs: Apply NFS_MOUNT_CMP_FLAGMASK to nfs_compare_remount_data()

Those flags are obsolete and checking them can incorrectly cause
remount operations to fail.

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>