[SCSI] qla2xxx: Move RISC-interrupt-register modifications to qla2x00_request_irqs().

There's no functional change involved with this update, instead
it simply migrates the "set cleared interrupt state" codes to a
more approprate method, qla2x00_request_irqs(), and cleans-up the
driver's probe() logic.

Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>