Add: Get channel payload support command

Implemented Get Channel Payload Support command (IPMI Spec sec 24.8)
The same is implemented under channel commands, and will be
available for both Host & Net ipmid. Uses channel configuration
to differentiate between session / session-less channel

Tested-by:
1. Verified command executed successfully for session
based channel
ipmitool raw 6 0x4E 0x1 // Command
03 00 15 00 00 00 00 00 // Response
2. Verified sessionless channel error is returned.

Change-Id: I8b294234415b4467aeae6c23c192750471536f4e
Signed-off-by: Saravanan Palanisamy <saravanan.palanisamy@intel.com>
Signed-off-by: Richard Marian Thomaiyar <richard.marian.thomaiyar@linux.intel.com>
diff --git a/user_channel/channel_layer.hpp b/user_channel/channel_layer.hpp
index 94570fb..1a8d64c 100644
--- a/user_channel/channel_layer.hpp
+++ b/user_channel/channel_layer.hpp
@@ -112,6 +112,24 @@
     oem = (1 << 0x5),
 };
 
+// TODO: Remove duplicate 'PayloadType' definition from netipmid's message.hpp
+// to phosphor-ipmi-host/include
+/**
+ * @enum Payload Types (refer spec sec 13.27.3)
+ */
+enum class PayloadType : uint8_t
+{
+    IPMI = 0x00,
+    SOL = 0x01,
+    OPEN_SESSION_REQUEST = 0x10,
+    OPEN_SESSION_RESPONSE = 0x11,
+    RAKP1 = 0x12,
+    RAKP2 = 0x13,
+    RAKP3 = 0x14,
+    RAKP4 = 0x15,
+    INVALID = 0xFF,
+};
+
 /**
  * @enum Access mode for channel access set/get (refer spec
  * sec 22.22 - request byte 2[7:6])