(A similar fix needs to be applied to the 3min and xine handlers.
This fixes a long-standing problem when booting with a card that
wants to interrupt (e.g., a network interface) would have interrupts
enabled before a handler was set up.
Add interrupt-counting code to model-independent interrupt handler,
and 3max (5k/200) and 3max+ (5k/240) md handlers, for vmstat -i.
Similar changes for 3min and xine are obvious but not done.
Add code for 5k/240 to read, and latch, the current value of the
IOASIC bus-cycle counter at each timer interrupt. The latched
counter is needed to accurately interpolate the bus-cycle counter value
as a high-resolution clock.