panfrost: Fix uniform_count on Midgard

panfrost: Fix uniform_count on Midgard

The compiler ABI specifies push uniforms at a 4-byte granularity (like
Bifrost), but Midgard require a 16-byte granularity. As such if the
number of pushed words is not a multiple of 4, there is a buffer overrun
at shader load time. Ordinarily this is inaccessible so the garbage is
ignored.

However, there was a great deal of confusion around the `uniform_cutoff`
variable. In some cases (such a full glmark2 run on a 64-bit processor),
the push uniforms would be at the end of a BO and the overrun would
cause a page fault.

Remove uniform_cutoff entirely and work with count directly to avoid
faulting, and round the count up to be defensive.

Closes: #4289
Fixes: ed810eb0a0c ("panfrost: Don't truncate uniform_count")
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Tested-by: Robin Murphy <robin.murphy@arm.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9109>