I have play by play data going back only to 1952, so this also an incomplete answer, but there have been 30 such incidences of back-to-back home runs, one tying the game, and one winning the game for teams in that time frame.
Here's a sampling from this decade:
July 26, 2017 - Blue Jays, Smoak/Morales
August 26, 2016 - Astros, Correa/Gattis
August 19, 2016 - Indians, Ramirez/Naquin (Naquin hit an inside-the-parkwalk-off home-run!)
June 18, 2014 - Red Sox, Ortiz/Napoli
May 19, 2013 - Phillies, Kratz/Galvis (both came off of Aroldis Chapman, one of only two multiple-HR-appearances by Chapman. The other came in 2016 against the Twins)
May 7, 2013 - Reds, Mesoraco/Choo (both off of Craig Kimbrel - the only multiple-HR-appearance in Kimbrel's career)
September 15, 2012 - Royals, Butler/Perez
Edit: Now, we have Christian Yelich/Ryan Braun for the Brewers on April 3, 2018!
Source: Retrosheet data - retrosheet.org.