The ornamental design for a scarfring, as shown and described.
1.1 : Front
1.2 : Left
1.3: Top
1.4: Top
1. Right view is omitted because it is identical with the left view; the broken lines showing a chain represent environment and form no part of the claimed design; the design consists of a scarf ring designed to tie and hold a scarf in place; top view no. 1.3 shows the scarf ring with the chain in the tight position; top view no. 1.4 shows the scarf ring with the chain in the loose position.