kselftest/arm64: Add a smoke test for ptracing hardware break/watch points

There was a report that the hardware breakpoints and watch points weren't
reporting the debug architecture version as expected, they were reporting
a version of 0 which is not defined in the architecture.  This happens
when running in a KVM guest if the host has a debug architecture version
not supported by KVM, it in turn confuses GDB which rejects any debug
architecture version it does not know about.

Add a test that covers that situation and while we're at it reports the
debug architecture version and number of slots available to aid with
figuring out problems that may arise.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230414-arm64-test-hw-breakpoint-v2-1-90a19e3b1059@kernel.org


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>