powerpc/82xx: Use common error handling code in pq2ads_pci_init_irq()

Adjust jump targets so that a bit of exception handling can be better
reused at the end of this function.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1a4bafee-562f-5eb4-d2bd-34704f8c5ab3@web.de