powerpc: Move include files to arch/powerpc/include/asm

from include/asm-powerpc.  This is the result of a

mkdir arch/powerpc/include/asm
git mv include/asm-powerpc/* arch/powerpc/include/asm

Followed by a few documentation/comment fixups and a couple of places
where <asm-powepc/...> was being used explicitly.  Of the latter only
one was outside the arch code and it is a driver only built for powerpc.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/boot/io.h b/arch/powerpc/boot/io.h
index ccaedae..7c09f48 100644
--- a/arch/powerpc/boot/io.h
+++ b/arch/powerpc/boot/io.h
@@ -6,7 +6,7 @@
 /*
  * Low-level I/O routines.
  *
- * Copied from <file:include/asm-powerpc/io.h> (which has no copyright)
+ * Copied from <file:arch/powerpc/include/asm/io.h> (which has no copyright)
  */
 static inline int in_8(const volatile unsigned char *addr)
 {