The concept of the IRQ isn't needed at this layer. The IRQ is something
which belongs to the particular hardware, not the innermost layer of the
kernel. Put another way intr_event is the device/interrupt source side
of the interrupt, "IRQs" are an interrupt controller concept.
This largely reverts commit 9b33b154b531606eccfc091faf50467eca0573f1.
Many places originally modified no longer exist and a number of new
locations have been added. This is still reverting a large portion of