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/doc/README.mpc85xxads b/doc/README.mpc85xxads
index ae8202b..046f981 100644
--- a/doc/README.mpc85xxads
+++ b/doc/README.mpc85xxads
@@ -124,8 +124,8 @@
     kernel's ppcboot.h is consistent with U-Boot's u-boot.h. You can use two
     default configuration files as your starting points to configure the
     kernel:
-	arch/ppc/configs/mpc8540_ads_defconfig
-	arch/ppc/configs/mpc8560_ads_defconfig
+	arch/powerpc/configs/mpc8540_ads_defconfig
+	arch/powerpc/configs/mpc8560_ads_defconfig
 
 3. DEFINITIONS AND COMPILATION