Makefile: rename all libraries to built-in.o

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/board/spd8xx/u-boot.lds b/board/spd8xx/u-boot.lds
index 2a68934..463af7e 100644
--- a/board/spd8xx/u-boot.lds
+++ b/board/spd8xx/u-boot.lds
@@ -18,8 +18,8 @@
 
     arch/powerpc/cpu/mpc8xx/start.o	(.text*)
     arch/powerpc/cpu/mpc8xx/traps.o	(.text*)
-    net/libnet.o			(.text*)
-    arch/powerpc/cpu/mpc8xx/libmpc8xx.o	(.text*)
+    net/built-in.o			(.text*)
+    arch/powerpc/cpu/mpc8xx/built-in.o	(.text*)
     *(.text.v*printf)
 
     . = DEFINED(env_offset) ? env_offset : .;