[port/sam] fix doxygen missing comment for init()
[port/sam] fix doxygen missing comment for init()

aethaniel/ExperimentalCore-sam,aethaniel/ExperimentalCore-sam,AloyseTech/ExperimentalCore-sam,logos-electromechanical/ExperimentalCore-sam,logos-electromechanical/ExperimentalCore-sam,AloyseTech/ExperimentalCore-sam,logos-electromechanical/ExperimentalCore-sam