powerpc/xive: Fix error handling when allocating an IPI

This is a smatch warning:

  arch/powerpc/sysdev/xive/common.c:1161 xive_request_ipi() warn: unsigned 'xid->irq' is never less than zero.

Fixes: fd6db289 ("powerpc/xive: Modernize XIVE-IPI domain with an 'alloc' handler")
Cc: stable@vger.kernel.org # v5.13
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210701152412.1507612-1-clg@kaod.org

arch/powerpc/sysdev/xive/common.c

@@ -1153,11 +1153,10 @@ static int __init xive_request_ipi(void)
 		 * Since the HW interrupt number doesn't have any meaning,
 		 * simply use the node number.
 		 */
-		xid->irq = irq_domain_alloc_irqs(ipi_domain, 1, node, &info);
-		if (xid->irq < 0) {
-			ret = xid->irq;
+		ret = irq_domain_alloc_irqs(ipi_domain, 1, node, &info);
+		if (ret < 0)
 			goto out_free_xive_ipis;
-		}
+		xid->irq = ret;
 
 		snprintf(xid->name, sizeof(xid->name), "IPI-%d", node);