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/kilauea.h b/include/configs/kilauea.h
index e5537da..48dc946 100644
--- a/include/configs/kilauea.h
+++ b/include/configs/kilauea.h
@@ -230,7 +230,7 @@
  *       SDRAM Controller DDR autocalibration values and takes a lot longer
  *       to run than Method_B.
  * (See the Method_A and Method_B algorithm discription in the file:
- *	arch/ppc/cpu/ppc4xx/4xx_ibm_ddr2_autocalib.c)
+ *	arch/powerpc/cpu/ppc4xx/4xx_ibm_ddr2_autocalib.c)
  * Define CONFIG_PPC4xx_DDR_METHOD_A to use DDR autocalibration Method_A
  *
  * DDR Autocalibration Method_B is the default.