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/stx/stxssa/stxssa.c b/board/stx/stxssa/stxssa.c
index 678ec58..0b2584c 100644
--- a/board/stx/stxssa/stxssa.c
+++ b/board/stx/stxssa/stxssa.c
@@ -259,7 +259,7 @@
 #endif
 
 	/* Why is the phy reset done _after_ the ethernet
-	 * initialization in arch/ppc/lib/board.c?
+	 * initialization in arch/powerpc/lib/board.c?
 	 * Do it here so it's done before the TSECs are used.
 	 */
 	reset_phy();