powerpc/ps3: Fix map failure path in dma_ioc0_map_pages()

powerpc/ps3: Fix map failure path in dma_ioc0_map_pages()

If lv1_put_iopte() fails in dma_ioc0_map_pages(), the error path
decrements iopage but keeps using the failed mapping's offset. As a
result, it repeatedly tries to invalidate the failed IOPTE slot and
leaves the already installed IOPTEs valid.

Recompute offset and invalidate the installed IOPTEs instead.

Fixes: 6bb5cf102541 ("[POWERPC] PS3: System-bus rework")
Cc: stable@vger.kernel.org
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260711130931.740719-3-thorsten.blum@linux.dev