COOK bacon and onions in Dutch oven or deep large skillet on medium heat 3 to 4 min. or until onions are crisp-tender, stirring occasionally. Add broth, potatoes and corn; stir. Bring to boil; simmer on medium-low heat 15 min. or until potatoes are tender.
MIX mayonnaise and flour in medium bowl with whisk until well blended. Gradually stir in milk. Add to ingredients in Dutch oven with turkey and salt; cook on medium heat 5 min. or until heated through and slightly thickened, stirring constantly. Remove from heat; stir in spinach.
SERVE topped with cheese.