ARM fixes for 6.16-rc1

- fix arch_memremap_can_ram_remap() which incorrectly passed a PFN to
  memblock_is_map_memory rather than the actual address.
- "Disallow kernel mode NEON when IRQs are disabled" - this needs a
  better explanation.

  "To avoid having to preserve/restore kernel mode NEON state when
  such a softirq is taken softirqs are now disabled when using the
  NEON from task context." should explain that it's nested kernel
  mode. In other words, softirqs from user mode are fine, because
  the context will be preserved. softirqs from kernel mode may
  be from a context that has already saved the user NEON state, and
  thus we would need to preserve the NEON state for the parent kernel
  mode context, and this we don't allow.

  The problem occurs when the kernel context disables hard IRQs, and
  then uses NEON. When it's finished, and restores the userspace NEON
  state, we call local_bh_enable() with hard IRQs disabled, which
  causes a warning.

  This commit addresses that by disallowing the use of NEON with hard
  IRQs disabled.

  https://lore.kernel.org/all/20250516231858.27899-4-ebiggers@kernel.org/T/#m104841b6e9346b1814c8b0fb9f2340551b0cd3e8
  has some further context.
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