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/jse/jse.c b/board/jse/jse.c
index e4c7b9d..fb39c84 100644
--- a/board/jse/jse.c
+++ b/board/jse/jse.c
@@ -26,7 +26,7 @@
 
 /*
  * This function is run very early, out of flash, and before devices are
- * initialized. It is called by arch/ppc/lib/board.c:board_init_f by virtue
+ * initialized. It is called by arch/powerpc/lib/board.c:board_init_f by virtue
  * of being in the init_sequence array.
  *
  * The SDRAM has been initialized already -- start.S:start called
@@ -85,7 +85,7 @@
 #endif
 
 /*
- * This function is also called by arch/ppc/lib/board.c:board_init_f (it is
+ * This function is also called by arch/powerpc/lib/board.c:board_init_f (it is
  * also in the init_sequence array) but later. Many more things are
  * configured, but we are still running from flash.
  */
@@ -149,7 +149,7 @@
 /* **** No more functions called by board_init_f. **** */
 
 /*
- * This function is called by arch/ppc/lib/board.c:board_init_r. At this
+ * This function is called by arch/powerpc/lib/board.c:board_init_r. At this
  * point, basic setup is done, U-Boot has been moved into SDRAM and
  * PCI has been set up. From here we done late setup.
  */
diff --git a/board/jse/sdram.c b/board/jse/sdram.c
index a12ebde..02eb6f2 100644
--- a/board/jse/sdram.c
+++ b/board/jse/sdram.c
@@ -27,7 +27,7 @@
 /*
  * this is even after checkboard. It returns the size of the SDRAM
  * that we have installed. This function is called by board_init_f
- * in arch/ppc/lib/board.c to initialize the memory and return what I
+ * in arch/powerpc/lib/board.c to initialize the memory and return what I
  * found.
  */
 phys_size_t initdram (int board_type)