nfsd: support NFS4_MAXMINOR up to the number an unsigned int can keep

This implementation allows specifying NFS4 minor version numbers up
to the number of bits available in int data type (typically 32 on
Linux)

This is based on an idea mentioned by
J. Bruce Fields <bfields@fieldses.org> mentioned on the linux-nfs mailing list.

I changed the data type back from an array to two bit fields, one for
storing whether the minor version was specified on the command line
and the second one for storing whether it was set or unset.  This
change was done to prevent blowing up the allocated stack space in an
unnecessary fashion.

Acked-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Robert Schiele <rschiele@gmail.com>
Signed-off-by: Steve Dickson <steved@redhat.com>