[SCSI] qla4xxx: Add spurious interrupt messages under debug level 2

The spurious interrupt messages are seen when interrupt lines are
shared between different adapters or modules. Example, interrupt
lines are shared between qlcnic and qla4xxx and USB modules, then the
console is flooded with flurry of spurious interrupt messages
which are expected in such scenario.

Hence put these messages under debug level 2 for INTx interrupt mode.

Signed-off-by: Nilesh Javali <nilesh.javali@qlogic.com>
Signed-off-by: Vikas Chaudhary <vikas.chaudhary@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>