x86/nmi: Fix comment in unknown_nmi_error()

x86/nmi: Fix comment in unknown_nmi_error()

The comment in unknown_nmi_error() is incorrect and misleading. There
is no longer a restriction on having a single Unknown NMI handler. Also,
nmi_handle() never used the 'b2b' parameter.

The commits that made the comment outdated are:

  0d443b70cc92 ("x86/platform: Remove warning message for duplicate NMI handlers")
  bf9f2ee28d47 ("x86/nmi: Remove the 'b2b' parameter from nmi_handle()")

Remove the old comment and update it to reflect the current logic.

Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Link: https://lore.kernel.org/r/20250327234629.3953536-6-sohil.mehta@intel.com