[PATCH] pata_octeon_cf: avoid WARN_ON() in ata_host_activate()

Iff platform_get_irq() fails (or returns IRQ0) and thus the polling mode
has to be used, ata_host_activate() hits the WARN_ON() due to 'irq_handler'
parameter being non-NULL if the polling mode is selected.  Let's only set
the pointer to the driver's IRQ handler if platform_get_irq() returns a
valid IRQ # -- this should avoid the unnecessary WARN_ON()...

Fixes: 3c929c6f5aa7 ("MIPS/OCTEON/ata: Convert pata_octeon_cf.c to use device tree.")
Signed-off-by: Sergey Shtylyov <redacted>

---
This patch is against the 'master' branch of Jens Axboe's 'linux-block.git'
repo.

 drivers/ata/pata_octeon_cf.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Index: linux-block/drivers/ata/pata_octeon_cf.c
===================================================================

--- linux-block.orig/drivers/ata/pata_octeon_cf.c
+++ linux-block/drivers/ata/pata_octeon_cf.c

@@ -898,10 +898,11 @@ static int octeon_cf_probe(struct platfo
 					return -EINVAL;
 				}
 
-				irq_handler = octeon_cf_interrupt;
 				i = platform_get_irq(dma_dev, 0);
-				if (i > 0)
+				if (i > 0) {
 					irq = i;
+					irq_handler = octeon_cf_interrupt;
+				}
 			}
 			of_node_put(dma_node);
 		}