The arraignment of Boston Police Commissioner Edward F. Davis’s son that was scheduled for Thursday in Plymouth, N.H., has been postponed until mid-March at his defense attorney’s request, according to the New Hampshire State Police. Philip Davis, 22, faces charges of driving while intoxicated two weeks ago in Plymouth. New Hampshire State Police spokeswoman Nicole Armaganian said the “defense requested and prosecution agreed to a continuance.” In a press release issued after the incident, State Police said that troopers stopped the vehicle Davis was driving at about 3 a.m. on High Street. Davis had five passengers with him, the statement said. The passengers were charged with being minors in possession of alcohol, State Police said.