Decode APIs now accept const struct pldm_msg *msg

All the decode_xxx APIs were changed to accept the complete pldm_msg
instead of working with just a specific member (payload) making it
consistent with the encode_xxx APIs.

Following changes were made through out the code,
 - decode_xxx now requires to send the const struct pldm_msg *msg
   instead of a const uint8_t *msg.
 - Within the decode_xxx function the payload is extracted and used
   accordingly.
 - All the calls made to decode_xxx APIs have been modified to now
   pass the pointer to pldm_msg_hdr (struct pldm_msg *msg).
 - The test code was modified to now pass the appropriate data
   to all the encode_xxx APIs.

Change-Id: I16a3f6e554ea2c9fa44d55dc8f21f65022bd983a
Signed-off-by: Zahed Hossain <zahzahed@in.ibm.com>
diff --git a/libpldm/platform.h b/libpldm/platform.h
index 7d25eb3..d29dc8a 100644
--- a/libpldm/platform.h
+++ b/libpldm/platform.h
@@ -117,7 +117,7 @@
 
 /** @brief Decode SetStateEffecterStates request data
  *
- *  @param[in] msg - Request message payload
+ *  @param[in] msg - Request message
  *  @param[in] payload_length - Length of request message payload
  *  @param[out] effecter_id - used to identify and access the effecter
  *  @param[out] comp_effecter_count - number of individual sets of effecter
@@ -133,7 +133,7 @@
  *  @return pldm_completion_codes
  */
 
-int decode_set_state_effecter_states_req(const uint8_t *msg,
+int decode_set_state_effecter_states_req(const struct pldm_msg *msg,
 					 size_t payload_length,
 					 uint16_t *effecter_id,
 					 uint8_t *comp_effecter_count,
@@ -166,12 +166,12 @@
 					 struct pldm_msg *msg);
 
 /** @brief Decode SetStateEffecterStates response data
- *  @param[in] msg - Request message payload
+ *  @param[in] msg - Request message
  *  @param[in] payload_length - Length of response message payload
  *  @param[out] completion_code - PLDM completion code
  *  @return pldm_completion_codes
  */
-int decode_set_state_effecter_states_resp(const uint8_t *msg,
+int decode_set_state_effecter_states_resp(const struct pldm_msg *msg,
 					  size_t payload_length,
 					  uint8_t *completion_code);
 #ifdef __cplusplus