hung_task: ignore hung_task_warnings when hung_task_panic is enabled

If hung_task_panic is enabled, don't consider the value of
hung_task_warnings and display the information of the hung tasks.

In some cases, hung_task_panic might not be initially set up, after
several hung tasks occur, the hung_task_warnings count reaches zero. If
hung_task_panic is set up later, it may not display any helpful hung task
info in dmesg, only showing messages like:

Kernel panic - not syncing: hung_task: blocked tasks
CPU: 3 PID: 58 Comm: khungtaskd Not tainted 6.10.0-rc3 #19
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
Call Trace:
<TASK>
panic+0x2f3/0x320
watchdog+0x2dd/0x510
? __pfx_watchdog+0x10/0x10
kthread+0xe0/0x110
? __pfx_kthread+0x10/0x10
ret_from_fork+0x2f/0x40
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
</TASK>

Link: https://lkml.kernel.org/r/20240613033159.3446265-1-leonylgao@gmail.com
Signed-off-by: Yongliang Gao <leonylgao@tencent.com>
Reviewed-by: Huang Cun <cunhuang@tencent.com>
Cc: Joel Granados <j.granados@samsung.com>
Cc: John Siddle <jsiddle@redhat.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>