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>

cpu/mpc5xxx/u-boot-customlayout.lds

@@ -58,8 +58,8 @@ SECTIONS
     cpu/mpc5xxx/start.o          (.text)
     cpu/mpc5xxx/traps.o          (.text)
     lib_generic/crc32.o         (.text)
-    lib_ppc/cache.o             (.text)
-    lib_ppc/time.o              (.text)
+    arch/ppc/lib/cache.o             (.text)
+    arch/ppc/lib/time.o              (.text)
 
     . = DEFINED(env_offset) ? env_offset : .;
     common/env_embedded.o        (.ppcenv)