portablectl: Strip .v or .raw.v when extracting prefix

This allows a plain "portablectl attach foobar.raw.v" without needing to
specify a prefix.

src/portable/portablectl.c

@@ -142,7 +142,7 @@ static int extract_prefix(const char *path, char **ret) {
         else {
                 const char *e;
 
-                e = endswith(bn, ".raw");
+                e = ENDSWITH_SET(bn, ".raw.v", ".raw", ".v");
                 if (!e)
                         e = strchr(bn, 0);