Move lib_$ARCH directories to arch/$ARCH/lib

Also move lib_$ARCH/config.mk to arch/$ARCH/config.mk

This change is intended to clean up the top-level directory structure
and more closely mimic Linux's directory organization.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>

board/sc3/u-boot.lds

@@ -70,7 +70,7 @@ SECTIONS
     cpu/ppc4xx/speed.o	(.text)
     common/dlmalloc.o	(.text)
     lib_generic/crc32.o		(.text)
-    lib_ppc/extable.o	(.text)
+    arch/ppc/lib/extable.o	(.text)
     lib_generic/zlib.o		(.text)
 
 /*    . = env_offset;*/