selftests/powerpc: Add ptrace tests for GPR/FPR registers

This patch adds ptrace interface test for GPR/FPR registers.
This adds ptrace interface based helper functions related to
GPR/FPR access and some assembly helper functions related to
GPR/FPR registers.

Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Simon Guo <wei.guo.simon@gmail.com>
[mpe: Add #defines for the new note types when headers don't define them]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>