powerpc: remove ADS860, FADS823, FADS850SAR, FADS860T support

Enough time has passed since these boards were moved to Orphan. Remove.

 - Remove include/configs/{ADS860.h,FADS823.h,FADS850SAR.h,FADS860T.h}
 - Cleanup defined(CONFIG_ADS), defined(CONFIG_MPC823FADS),
   defined(CONFIG_MPC850SAR), defined(CONFIG_SYS_DAUGHTERBOARD)
 - Remove the entries from boards.cfg

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/arch/powerpc/cpu/mpc8xx/serial.c b/arch/powerpc/cpu/mpc8xx/serial.c
index cb48ed9..f7ca11e 100644
--- a/arch/powerpc/cpu/mpc8xx/serial.c
+++ b/arch/powerpc/cpu/mpc8xx/serial.c
@@ -173,7 +173,7 @@
 # endif
 #endif
 
-#if defined(CONFIG_FADS) || defined(CONFIG_ADS)
+#if defined(CONFIG_FADS)
 	/* Enable RS232 */
 #if defined(CONFIG_8xx_CONS_SMC1)
 	*((uint *) BCSR1) &= ~BCSR1_RS232EN_1;