powerpc/powernv/pci: Fix underflow and leak issue

pnv_irq_domain_alloc() allocates interrupts at parent's interrupt
domain. If it fails in the progress, all allocated interrupts are
freed.

The number of successfully allocated interrupts so far is stored
"i". However, "i - 1" interrupts are freed. This is broken:

- One interrupt is not be freed

- If "i" is zero, "i - 1" wraps around

Correct the number of freed interrupts to "i".

Fixes: 0fcfe2247e75 ("powerpc/powernv/pci: Add MSI domains")
Signed-off-by: Nam Cao <[e-mail]>
Cc: [e-mail]
Reviewed-by: Cédric Le Goater <[e-mail]>
Signed-off-by: Madhavan Srinivasan <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

arch/powerpc/platforms/powernv/pci-ioda.c

···
 	return 0;
 
 out:
-	irq_domain_free_irqs_parent(domain, virq, i - 1);
+	irq_domain_free_irqs_parent(domain, virq, i);
 	msi_bitmap_free_hwirqs(&phb->msi_bmp, hwirq, nr_irqs);
 	return ret;
 }