lib/nmi_backtrace: print out the CPUs which fail to respond to NMI

lib/nmi_backtrace: print out the CPUs which fail to respond to NMI

When debugging RCU stall cases, usually all CPUs will respond to the NMI
and print out the backtrace.  But in some nasty or hardware related cases,
some CPUs may fail to respond in 10 seconds, and very likely this is sign
of severe issues.

Paul McKenney has implemented the NMI backtrace stall check for x86, and
for other architectures, it should be also helpful to at least print out
those CPUs which failed to repond to the NMI, so that users can get an
early heads-up for possible CPU hard stall.

[feng.tang@linux.alibaba.com: avoid hard-coding "10" in two places and in a comment]
Link: https://lore.kernel.org/ag-1ciG0FSomBf7q@U-2FWC9VHC-2323.local
[akpm@linux-foundation.org: use __stringify()]
Link: https://lore.kernel.org/20260521030336.92172-1-feng.tang@linux.alibaba.com
Signed-off-by: Feng Tang <feng.tang@linux.alibaba.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>