[platform][rosco-m68k] microoptimize the duart irq
[platform][rosco-m68k] microoptimize the duart irq

hollanderic/lkstuff,hollanderic/lkstuff,hollanderic/lkstuff,littlekernel/lk,littlekernel/lk,littlekernel/lk,hollanderic/lkstuff,littlekernel/lk