Fix maximum SSIF message size

As IPMI spec, the maximum SSIF message size is 255 bytes.

Signed-off-by: Dung Cao <dung@os.amperecomputing.com>
Change-Id: I59c4390616dff5ed372b4e7d8595435f41f423ee
diff --git a/ssifbridged.cpp b/ssifbridged.cpp
index 2f7bf3d..12f8e99 100644
--- a/ssifbridged.cpp
+++ b/ssifbridged.cpp
@@ -41,7 +41,7 @@
 class SsifChannel
 {
   public:
-    static constexpr size_t ssifMessageSize = 4096;
+    static constexpr size_t ssifMessageSize = 255;
     static constexpr uint8_t netFnShift = 2;
     static constexpr uint8_t lunMask = (1 << netFnShift) - 1;