powerpc: Remove <common.h> and add needed includes

Remove <common.h> from all powerpc architecture files and when needed add
missing include files directly. This typically involves using
<asm/u-boot.h> instead due to the difficult nested structure of the
PowerPC includes themselves.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/powerpc/cpu/mpc83xx/speed.c b/arch/powerpc/cpu/mpc83xx/speed.c
index b7a87fe..bfc6242 100644
--- a/arch/powerpc/cpu/mpc83xx/speed.c
+++ b/arch/powerpc/cpu/mpc83xx/speed.c
@@ -8,7 +8,7 @@
 
 #ifndef CONFIG_CLK_MPC83XX
 
-#include <common.h>
+#include <asm/u-boot.h>
 #include <clock_legacy.h>
 #include <mpc83xx.h>
 #include <command.h>