with shared IRQs in case the bus code, MD interrupt code, etc. permits.
Together with sys/sparc64/sparc64/intr_machdep.c rev. 1.21 this fixes
an endless loop in uart_intr() when using the second NS16550 on the ISA
bus of sparc64 machines.
- Destroy the hardware mutex on detach and in case attaching fails.
Approved by: marcel