POST cleanup.

POST cleanup.

- Revives POST for blackfin arch;
- Removes redundant code:
     arch/blackfin/lib/post.c
     arch/powerpc/cpu/ppc4xx/commproc.c
     arch/powerpc/cpu/mpc512x/common.c
- fixes up the post_word_{load|store} usage.

Signed-off-by: Michael Zaidman <[email protected]>
Acked-by: Detlev Zundel <[email protected]>
Tested-by: Anatolij Gustschin <[email protected]>
List of the maintainers of the affected by patch boards:
Cc: Stephan Linz <[email protected]>
Cc: Denis Peter <[email protected]>
Cc: Matthias Fuchs <[email protected]>
Cc: Peter Tyser <[email protected]>
Cc: Stefan Roese <[email protected]>
Cc: Mike Frysinger <[email protected]>
Cc: Niklaus Giger <[email protected]>
Cc: Larry Johnson <[email protected]>
Cc: Feng Kan <[email protected]>