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/xilinx/ppc405-generic/u-boot-rom.lds b/board/xilinx/ppc405-generic/u-boot-rom.lds
index 8fafbd5..65d0e4d 100644
--- a/board/xilinx/ppc405-generic/u-boot-rom.lds
+++ b/board/xilinx/ppc405-generic/u-boot-rom.lds
@@ -33,7 +33,7 @@
 
   .bootpg 0xFFFFF000 :
   {
-    arch/ppc/cpu/ppc4xx/start.o	(.bootpg)
+    arch/powerpc/cpu/ppc4xx/start.o	(.bootpg)
   } = 0xffff
 
   /* Read-only sections, merged into text segment: */