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/include/configs/linkstation.h b/include/configs/linkstation.h
index 3958d09..6883e79 100644
--- a/include/configs/linkstation.h
+++ b/include/configs/linkstation.h
@@ -290,7 +290,7 @@
  * taken from the orignal Linkstation boot code
  *
  * Most of the low level configuration setttings are normally used
- * in arch/ppc/cpu/mpc824x/cpu_init.c which is NOT used by this implementation.
+ * in arch/powerpc/cpu/mpc824x/cpu_init.c which is NOT used by this implementation.
  * Low level initialisation is done in board/linkstation/early_init.S
  * The values below are included for reference purpose only
  */