modules: tfm: cleanup redundant Kconfig symbol selection

When we select BUILD_WITH_TFM we do not
really need to enable by default the
options THREAD_NAME, THREAD_STACK_INFO,
INIT_STACKS and THREAD_MONITOR, so we can
clean them up. We also remove CMSIS_RTOS_V2
for the same reason.

We also cleanup the default value for
NUM_PREEMPT_PRIORITIES, which does not
seem to be needed.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>