api: refactor to use REPLY_MSG_ID_BASE #define

REPLY_MSG_ID_BASE is the standard way to define reply message id base,
so this refactor makes all the files use that. This is a preparation
patch for future safety add-ons which rely on REPLY_MACRO* parameters to
be preprocessor tokens identifying the message instead,

Type: refactor
Signed-off-by: Klement Sekera <ksekera@cisco.com>
Change-Id: Ibe3e056a3d9326d08af45bbcb25588b11e870141