hpsa: rename hpsa_request_irq to hpsa_request_irqs

Make the function name more descriptive. We use more than
one interrupt.

Reviewed-by: Scott Teel <scott.teel@pmcs.com>
Signed-off-by: Robert Elliott <elliott@hp.com>
Signed-off-by: Don Brace <don.brace@pmcs.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>