Move arch/ppc to arch/powerpc

As discussed on the list, move "arch/ppc" to "arch/powerpc" to
better match the Linux directory structure.

Please note that this patch also changes the "ppc" target in
MAKEALL to "powerpc" to match this new infrastructure. But "ppc"
is kept as an alias for now, to not break compatibility with
scripts using this name.

Signed-off-by: Stefan Roese <sr@denx.de>
Acked-by: Wolfgang Denk <wd@denx.de>
Acked-by: Detlev Zundel <dzu@denx.de>
Acked-by: Kim Phillips <kim.phillips@freescale.com>
Cc: Peter Tyser <ptyser@xes-inc.com>
Cc: Anatolij Gustschin <agust@denx.de>
diff --git a/board/logicpd/zoom2/zoom2_serial.c b/board/logicpd/zoom2/zoom2_serial.c
index cfbad13..fcfe624 100644
--- a/board/logicpd/zoom2/zoom2_serial.c
+++ b/board/logicpd/zoom2/zoom2_serial.c
@@ -17,7 +17,7 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  * MA 02111-1307 USA
  *
- * This file was adapted from arch/ppc/cpu/mpc5xxx/serial.c
+ * This file was adapted from arch/powerpc/cpu/mpc5xxx/serial.c
  *
  */