arm64: smp: Add arch support for backtrace using pseudo-NMI

arm64: smp: Add arch support for backtrace using pseudo-NMI

Enable arch_trigger_cpumask_backtrace() support on arm64. This enables
things much like they are enabled on arm32 (including some of the
funky logic around NR_IPI, nr_ipi, and MAX_IPI) but with the
difference that, unlike arm32, we'll try to enable the backtrace to
use pseudo-NMI.

NOTE: this patch is a squash of the little bit of code adding the
ability to mark an IPI to try to use pseudo-NMI plus the little bit of
code to hook things up for kgdb. This approach was decided upon in the
discussion of v9 [1].

This patch depends on commit 8d539b84f1e3 ("nmi_backtrace: allow
excluding an arbitrary CPU") since that commit changed the prototype
of arch_trigger_cpumask_backtrace(), which this patch implements.

[1] https://lore.kernel.org/r/ZORY51mF4alI41G1@FVFF77S0Q05N

Co-developed-by: Sumit Garg <[email protected]>
Signed-off-by: Sumit Garg <[email protected]>
Co-developed-by: Mark Rutland <[email protected]>
Signed-off-by: Mark Rutland <[email protected]>
Reviewed-by: Stephen Boyd <[email protected]>
Reviewed-by: Misono Tomohiro <[email protected]>
Tested-by: Chen-Yu Tsai <[email protected]>
Signed-off-by: Douglas Anderson <[email protected]>
Link: https://lore.kernel.org/r/20230906090246.v13.4.Ie6c132b96ebbbcddbf6954b9469ed40a6960343c@changeid
Signed-off-by: Catalin Marinas <[email protected]>