powerpc: Make some #includes explicit.

In preparation for merging processor.h, this adds some explicit
but won't be after the merge.

Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/ppc/kernel/pci.c b/arch/ppc/kernel/pci.c
index b5cf52f..6600fd4 100644
--- a/arch/ppc/kernel/pci.c
+++ b/arch/ppc/kernel/pci.c
@@ -21,6 +21,7 @@
 #include <asm/byteorder.h>
 #include <asm/irq.h>
 #include <asm/uaccess.h>
+#include <asm/machdep.h>
 
 #undef DEBUG