x86/nmi: Fix nmi_handle() duration miscalculation

x86/nmi: Fix nmi_handle() duration miscalculation

When nmi_check_duration() is checking the time an NMI handler took to
execute, the whole_msecs value used should be read from the @duration
argument, not from the ->max_duration, the latter being used to store
the current maximal duration.

 [ bp: Rewrite commit message. ]

Fixes: bb3155a33155 ("x86/nmi: Remove irq_work from the long duration NMI handler")
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Libing Zhou <libing.zhou@nokia-sbell.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Changbin Du <changbin.du@gmail.com>
Link: https://lkml.kernel.org/r/20200820025641.44075-1-libing.zhou@nokia-sbell.com