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/mbx8xx/vpd.c b/board/mbx8xx/vpd.c
index 3bc251d..1c99fd6 100644
--- a/board/mbx8xx/vpd.c
+++ b/board/mbx8xx/vpd.c
@@ -3,7 +3,7 @@
  * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
  * Marius Groeger <mgroeger@sysgo.de>
  *
- * Code in faintly related to linux/arch/ppc/8xx_io:
+ * Code in faintly related to linux/arch/powerpc/8xx_io:
  * MPC8xx CPM I2C interface. Copyright (c) 1999 Dan Malek (dmalek@jlc.net).
  *
  * This file implements functions to read the MBX's Vital Product Data