Rename lib_generic/ to lib/

Now that the other architecture-specific lib directories have been
moved out of the top-level directory there's not much reason to have the
'_generic' suffix on the common lib directory.

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

board/astro/mcf5373l/u-boot.lds

@@ -59,7 +59,7 @@ SECTIONS
     arch/m68k/lib/traps.o		(.text)
     arch/m68k/lib/interrupts.o	(.text)
     common/dlmalloc.o		(.text)
-    lib_generic/zlib.o		(.text)
+    lib/zlib.o		(.text)
 
     . = DEFINED(env_offset) ? env_offset : .;
     common/env_embedded.o	(.text)