rcutorture: Remove MAXSMP and CPUMASK_OFFSTACK from TREE01

Back in the day, rcutorture was about the only thing that tested off-stack
CPU masks, but now any arm64 system with more than 256 CPUs tests it
full time.  In fact, it is necessary to hack the kernel to prevent such
a system from testing off-stack CPU masks.  This means that there is
no longer much point in rcutorture going out of its way to test this.
And given the differences in how CPUMASK_OFFSTACK is enabled in x86 and
arm64, rcutorture would need to go out of its way.

This commit therefore removes CONFIG_CPUMASK_OFFSTACK=y (and the
CONFIG_MAXSMP=y required to enable it on x86) from TREE01.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>