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/aria.h b/include/configs/aria.h
index 06763c5..b6669e7 100644
--- a/include/configs/aria.h
+++ b/include/configs/aria.h
@@ -190,7 +190,7 @@
 
 /*
  * Backward compatible definitions,
- * so we do not have to change arch/ppc/cpu/mpc512x/fixed_sdram.c
+ * so we do not have to change arch/powerpc/cpu/mpc512x/fixed_sdram.c
  */
 #define	CONFIG_SYS_DDRCMD_EM2		(CONFIG_SYS_MICRON_EMR2)
 #define CONFIG_SYS_DDRCMD_EM3		(CONFIG_SYS_MICRON_EMR3)