raw/ifpga/base: fix return of IRQ unregister

Since 'rte_intr_callback_unregister()' can return positive
value as success, but 'ifpga_rawdev_destroy()' handle it as
an error.

Instead, only negative return is treated as failure.

Fixes: e0a1aafe2af9 ("raw/ifpga: introduce IRQ functions")
Cc: stable@dpdk.org

Signed-off-by: Wei Huang <wei.huang@intel.com>
Signed-off-by: Tianfei Zhang <tianfei.zhang@intel.com>
Acked-by: Rosen Xu <rosen.xu@intel.com>

drivers/raw/ifpga/ifpga_rawdev.c

@@ -1559,7 +1559,7 @@ ifpga_rawdev_destroy(struct rte_pci_device *pci_dev)
 		return -ENODEV;
 
 	if (ifpga_unregister_msix_irq(IFPGA_FME_IRQ, 0,
-				fme_interrupt_handler, mgr))
+				fme_interrupt_handler, mgr) < 0)
 		return -EINVAL;
 
 	opae_adapter_data_free(adapter->data);