drm/msm/dpu: fix the irq index in dpu_encoder_phys_wb_wait_for_commit_done

drm/msm/dpu: fix the irq index in dpu_encoder_phys_wb_wait_for_commit_done

Since commit 1e7ac595fa46 ("drm/msm/dpu: pass irq to
dpu_encoder_helper_wait_for_irq()") the
dpu_encoder_phys_wb_wait_for_commit_done expects the IRQ index rather
than the IRQ index in phys_enc->intr table, however writeback got the
older invocation in place. This was unnoticed for several releases, but
now it's time to fix it.

Fixes: d7d0e73f7de3 ("drm/msm/dpu: introduce the dpu_encoder_phys_* for writeback")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/550924/
Link: https://lore.kernel.org/r/20230802100426.4184892-2-dmitry.baryshkov@linaro.org