I noticed while looking at some traces, that we could miss calls to
msm_update_fence(), as the irq could have raced with retire_submits()
which could have already popped the last submit on a ring out of the
queue of in-flight submits.  But walking the list of submits in the
irq handler isn't really needed, as dma_fence_is_signaled() will dtrt.
So lets just drop it entirely.

v2: use spin_lock_irqsave/restore as we are no longer protected by the
    spin_lock_irqsave/restore() in update_fences()
Reported-by: Steev Klimaszewski <steev@kali.org>
Fixes: 95d1deb0 ("drm/msm/gem: Add fenced vma unpin")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Tested-by: Steev Klimaszewski <steev@kali.org>
Patchwork: https://patchwork.freedesktop.org/patch/490136/
Link: https://lore.kernel.org/r/20220618161120.3451993-1-robdclark@gmail.com