riscv: ax25-ae350: doc: Fix minor format issues

This fixes two minor format issues of the ax25-ae350 reST file.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Rick Chen <rick@andestech.com>
diff --git a/doc/board/AndesTech/ax25-ae350.rst b/doc/board/AndesTech/ax25-ae350.rst
index f795476..9236492 100644
--- a/doc/board/AndesTech/ax25-ae350.rst
+++ b/doc/board/AndesTech/ax25-ae350.rst
@@ -343,7 +343,7 @@
         cd opensbi
         make PLATFORM=andes/ae350
 
-Copy OpenSBI FW_DYNAMIC image (build\platform\andes\ae350\firmware\fw_dynamic.bin)
+Copy OpenSBI FW_DYNAMIC image (build/platform/andes/ae350/firmware/fw_dynamic.bin)
 into U-Boot root directory
 
 
@@ -532,4 +532,4 @@
     Sat Apr  6 23:33:53 CST 2019
     nfs4flexfilelayout_init: NFSv4 Flexfile Layout Driver Registering...
 
-~ #
+    ~ #