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/gen860t/ioport.c b/board/gen860t/ioport.c
index 146573e..8d46925 100644
--- a/board/gen860t/ioport.c
+++ b/board/gen860t/ioport.c
@@ -197,7 +197,7 @@
 
 /*
  * Configure the MPC8XX I/O ports per the ioport configuration table
- * (taken from ./arch/ppc/cpu/mpc8260/cpu_init.c)
+ * (taken from ./arch/powerpc/cpu/mpc8260/cpu_init.c)
  */
 void config_mpc8xx_ioports (volatile immap_t * immr)
 {