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: fd6db2892eba ("powerpc/xive: Modernize XIVE-IPI domain with an 'alloc' handler")
Cc: [e-mail] # v5.13
Reported-by: kernel test robot <[e-mail]>
Signed-off-by: Cédric Le Goater <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/powerpc/sysdev/xive/common.c

···
 		 * 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);