selftests/powerpc: Add ptrace hw breakpoint test

selftests/powerpc: Add ptrace hw breakpoint test

[ Upstream commit 9c2ddfe55c42bf4b9bc336a0650ab78f9222a159 ]

This test the ptrace hw breakpoints via PTRACE_SET_DEBUGREG and
PPC_PTRACE_SETHWDEBUG.  This test was use to find the bugs fixed by
these recent commits:

  4f7c06e26e powerpc/ptrace: Fix setting 512B aligned breakpoints with PTRACE_SET_DEBUGREG
  cd6ef7eebf powerpc/ptrace: Fix enforcement of DAWR constraints

Signed-off-by: Michael Neuling <mikey@neuling.org>
[mpe: Add SPDX tag, clang format it]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>