From: "Nakajima, Jun" <jun.nakajima@intel.com>

To get the vector-based interrupt handling work, we need to give the vector
number to device drivers instead of the IRQ if IRQ < 16.  It was not
happening for SCI, and the patch fixes it.  In many cases, the IRQ for SCI is
9, and the problem was not detected, but one particular machine exposed the
bug.