powerpc: mpc8xx: remove SXNI855T board support

This board has been orphaned for a while and old enough.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/CREDITS b/CREDITS
index 3e5fb7b..43d4764 100644
--- a/CREDITS
+++ b/CREDITS
@@ -126,7 +126,7 @@
 
 N: Dave Ellis
 E: DGE@sixnetio.com
-D: EEPROM Speedup, SXNI855T port
+D: EEPROM Speedup
 
 N: Daniel Engstr?m
 E: daniel@omicron.se