powerpc, 5xxx, 512x: remove support for mpc5xxx and mpc512x

There was for long time no activity in the mpx5xxx area.
We need to go further and convert to Kconfig, but it
turned out, nobody is interested anymore in mpc5xxx,
so remove it.

Signed-off-by: Heiko Schocher <hs@denx.de>
diff --git a/include/keyboard.h b/include/keyboard.h
index 5cbd9f8..9b51e20 100644
--- a/include/keyboard.h
+++ b/include/keyboard.h
@@ -98,7 +98,7 @@
 extern void pckbd_leds(unsigned char leds);
 #endif /* !CONFIG_DM_KEYBOARD */
 
-#if defined(CONFIG_MPC5xxx) || defined(CONFIG_ARCH_MPC8540) || \
+#if defined(CONFIG_ARCH_MPC8540) || \
 		defined(CONFIG_ARCH_MPC8541) || defined(CONFIG_ARCH_MPC8555)
 int ps2ser_check(void);
 #endif