Makefile: Define arch dependent sources explicitly
Makefile: Define arch dependent sources explicitly

This enables "make dist" to include all the arch sources.

Signed-off-by: Amitay Isaacs <a505e7c038746dbeb3edcd8d146dbd515432801f@ozlabs.org>

open-power/pdbg,open-power/pdbg,open-power/pdbg