x86/mce: Restore MCA polling interval halving

x86/mce: Restore MCA polling interval halving

RongQing reported that the MCA polling interval doesn't halve when an
error gets logged. It was traced down to the commit in Fixes:, because:

  mce_timer_fn()
  |-> mce_poll_banks()
  |-> machine_check_poll()
  |-> mce_log()

which will queue the work and return.

Now, back in mce_timer_fn():

        /*
         * Alert userspace if needed. If we logged an MCE, reduce the polling
         * interval, otherwise increase the polling interval.
         */
        if (mce_notify_irq())

<--- here we haven't ran the notifier chain yet so mce_need_notify is
not set yet so this won't hit and we won't halve the interval iv.

Now the notifier chain runs. mce_early_notifier() sets the bit, does
mce_notify_irq(), that clears the bit and then the notifier chain
a little later logs the error.

So this is a silly timing issue.

But, that's all unnecessary.

All it needs to happen here is, the "should we notify of a logged MCE"
mce_notify_irq() asks, should be simply a question to the mce gen pool:
"Are you empty?"

And that then turns into a simple yes or no answer and it all
JustWorks(tm).

So do that and also distribute the functionality where it belongs:
 - Print that MCE events have been logged in mce_log()
 - Trigger the mcelog tool specific work in the first notifier

As a result, mce_notify_irq() can go now.

Fixes: 011d82611172 ("RAS: Add a Corrected Errors Collector")
Reported-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Tested-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Link: https://lore.kernel.org/r/20260112082747.2842-1-lirongqing@baidu.com