system: add floppy bootindex for q35

Other targets will not have bootorder but they will not be used often.

Fixes #2492

Author: osy

Managers/UTMQemuSystem.m

@@ -192,6 +192,11 @@ - (NSString *)expandDriveInterface:(NSString *)interface identifier:(NSString *)
     } else if ([interface isEqualToString:@"usb"]) {
         [self pushArgv:@"-device"];
         [self pushArgv:[NSString stringWithFormat:@"usb-storage,drive=%@,removable=%@,bootindex=%lu", identifier, removable ? @"true" : @"false", bootindex++]];
+    } else if ([interface isEqualToString:@"floppy"] && [self.configuration.systemTarget hasPrefix:@"q35"]) {
+        [self pushArgv:@"-device"];
+        [self pushArgv:[NSString stringWithFormat:@"isa-fdc,id=fdc%lu,bootindexA=%lu", busindex, bootindex++]];
+        [self pushArgv:@"-device"];
+        [self pushArgv:[NSString stringWithFormat:@"floppy,unit=0,bus=fdc%lu.0,drive=%@", busindex++, identifier]];
     } else {
         return interface; // no expand needed
     }