rcutorture: Fix issue with re-using old images on ARM64

On ARM64, when running with --configs '36*SRCU-P', I noticed that only 1 instance
instead of 36 for starting.

Fix it by checking for Image files, instead of bzImage which ARM does
not seem to have. With this I see all 36 instances running at the same
time in the batch.

Tested-by: Paul E. McKenney <[e-mail]>
Signed-off-by: Joel Fernandes <[e-mail]>

tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh

···
 cp $T/KcList $resdir/ConfigFragment
 
 base_resdir=`echo $resdir | sed -e 's/\.[0-9]\+$//'`
-if test "$base_resdir" != "$resdir" && test -f $base_resdir/bzImage && test -f $base_resdir/vmlinux
+if test "$base_resdir" != "$resdir" && (test -f $base_resdir/bzImage || test -f $base_resdir/Image) && test -f $base_resdir/vmlinux
 then
 	# Rerunning previous test, so use that test's kernel.
 	QEMU="`identify_qemu $base_resdir/vmlinux`"