mpc83xx: clean up the readme for 83xx boards

1. correct the typo
2. correct the memory map for 837xerdb board

Signed-off-by: Dave Liu <daveliu@freescale.com>
diff --git a/doc/README.mpc8313erdb b/doc/README.mpc8313erdb
index 7ad4cc7..21580f9 100644
--- a/doc/README.mpc8313erdb
+++ b/doc/README.mpc8313erdb
@@ -3,10 +3,10 @@
 
 1.	Board Switches and Jumpers
 
-	SW3 is used to set CFG_RESET_SOURCE.
+	S3 is used to set CFG_RESET_SOURCE.
 
 	To boot the image at 0xFE000000 in NOR flash, use these DIP
-	switche settings for SW3 SW4:
+	switch settings for S3 S4:
 
 	+------+	+------+
 	|      |	| **** |