libpldm : add encode/decode APIs for SetStateEffecterStates

This commit implements the encode request and decode
response APIs for the SetStateEffecterStates command.
This enables BMC requester apps to send this command and
process the received response.

Change-Id: I1436c8730553b5a1aed8cda1fa90b8742e5be228
Signed-off-by: vkaverap <vkaverap@in.ibm.com>