selftests/powerpc: Make git ignore all binaries in powerpc test suite

This patch includes all of the powerpc test binaries into the .gitignore
file listing in their respective directories. This will make sure that
git ignores all of these test binaries when displaying status.

Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>