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>
diff --git a/board/freescale/m54451evb/u-boot.spa b/board/freescale/m54451evb/u-boot.spa
index d8caefa..569518b 100644
--- a/board/freescale/m54451evb/u-boot.spa
+++ b/board/freescale/m54451evb/u-boot.spa
@@ -57,7 +57,7 @@
 
     cpu/mcf5445x/start.o		(.text)
     cpu/mcf5445x/libmcf5445x.a	(.text)
-    lib_m68k/libm68k.a		(.text)
+    arch/m68k/lib/libm68k.a		(.text)
     common/cmd_flash.o		(.text)
     common/dlmalloc.o		(.text)
     common/main.o		(.text)