Revert "perf/aux: Allocate non-contiguous AUX pages by default"

This reverts commit 18049c8cff9cc89daadc4df6975f7d9069638926.

The original commit claimed that contiguous AUX pages unnecessarily
exacerbate fragmentation for SPE, TRBE and ETR. This is not generally
valid: larger allocations can keep pages with the same lifetime
together, while order-0 allocations can scatter them across large
blocks and prevent free pages from coalescing [1]. The follow-up
discussion [2] has not established how forcing order-0 allocations
addresses the reported problem.

TRBE and SPE write to virtually addressed buffers. The TRBE L1 TLB
has one entry on Neoverse V2 [3] and two on Neoverse V3 [4]. Small
mappings increase translation pressure, and TTW stalls can contribute
to FIFO overflow and trace loss on TRBE.

Larger allocations provide contiguous, aligned chunks for PMD or
contiguous-PTE mappings with the proposed vmap() support [5].
With the proposed vmap() support already applied, the tests in [2]
showed that preferring larger AUX allocations reduced L2 data TLB
refills by 99.68% in the TRBE test and 34.74% in the SPE test.

Restore the previous policy of trying higher-order allocations first.
The allocator already uses __GFP_NORETRY and falls back to smaller
orders, including order 0, when larger allocations fail.

Remove PERF_PMU_CAP_AUX_PREFER_LARGE, since the restored default
provides that preference. Intel PT retains its existing allocation
behaviour, with no functional change.

[1] https://lore.kernel.org/all/aPjrRkjiIt6HmXmT@casper.infradead.org/
[2] https://lore.kernel.org/linux-arm-kernel/20260810-perf_aux_trace_large_granule-v1-0-03306c9339e3@arm.com/
[3] https://documentation-service.arm.com/static/633fe1ec4c59b30b517730b8#page=52
[4] https://documentation-service.arm.com/static/67361bd2c7fc0d1f211da382#page=54
[5] https://lore.kernel.org/linux-mm/20260715120813.3609949-1-jiangwen6@xiaomi.com/

Signed-off-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: James Clark <james.clark@linaro.org>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Link: https://patch.msgid.link/20261025-perf_revert_prefer_large_alloc-v1-1-5fb431bbd624@arm.com

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