post: Remove references to scrapped "netta" board.

Given that README.scrapyard shows scrapping of netta boards:

netta2           powerpc     mpc8xx         c51c1c9a    2014-07-07
netta            powerpc     mpc8xx         c51c1c9a    2014-07-07

delete netta example from POST tests.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>

post/Makefile

@@ -13,6 +13,6 @@ obj-$(CONFIG_PPC) += lib_powerpc/
 obj-$(CONFIG_MPC83xx) += cpu/mpc83xx/
 obj-$(CONFIG_8xx) += cpu/mpc8xx/
 obj-$(CONFIG_4xx) += cpu/ppc4xx/
-ifneq ($(filter lwmon5 netta pdm360ng,$(BOARD)),)
+ifneq ($(filter lwmon5 pdm360ng,$(BOARD)),)
 obj-y += board/$(BOARD)/
 endif

post/board/netta/Makefile

-#
-# (C) Copyright 2002-2006
-# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
-#
-# SPDX-License-Identifier:	GPL-2.0+
-#
-
-obj-y += codec.o dsp.o

post/board/netta/codec.c

-/*
- * (C) Copyright 2004
- * Pantelis Antoniou, Intracom S.A. , panto@intracom.gr
- *
- * SPDX-License-Identifier:	GPL-2.0+
- */
-
-#include <common.h>
-
-/*
- * CODEC test
- *
- * This test verifies the connection and performs a memory test
- * on any connected codec(s). The meat of the work is done
- * in the board specific function.
- */
-
-#include <post.h>
-
-#if CONFIG_POST & CONFIG_SYS_POST_CODEC
-
-extern int board_post_codec(int flags);
-
-int codec_post_test (int flags)
-{
-	return board_post_codec(flags);
-}
-
-#endif /* CONFIG_POST & CONFIG_SYS_POST_CODEC */

post/board/netta/dsp.c

-/*
- * (C) Copyright 2004
- * Pantelis Antoniou, Intracom S.A. , panto@intracom.gr
- *
- * SPDX-License-Identifier:	GPL-2.0+
- */
-
-#include <common.h>
-
-/*
- * DSP test
- *
- * This test verifies the connection and performs a memory test
- * on any connected DSP(s). The meat of the work is done
- * in the board specific function.
- */
-
-#include <post.h>
-
-#if CONFIG_POST & CONFIG_SYS_POST_DSP
-
-extern int board_post_dsp(int flags);
-
-int dsp_post_test (int flags)
-{
-	return board_post_dsp(flags);
-}
-
-#endif /* CONFIG_POST & CONFIG_SYS_POST_DSP */