docs: fix warnings in doc creation

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
Doxygen: add layout file and make formatting more sensible

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
max31723: improve documentation

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>