ARC: SMP: fix livelock in thread abort due to exception

We are missing setting of switch_handle for the thread which
is aborting due to exception (i.e. in case of k_panic or
__ASSERT triggered). This may cause livelock in SMP code
after a08e23f6 commit ("kernel/sched: Fix SMP
must-wait-for-switch conditions in abort/join").

Fix that.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Evgeniy Paltsev <PaltsevEvgeniy@gmail.com>