gpu: nova-core: add the per-architecture GIN CPU interrupt HAL

The GIN CPU interrupt tree differs by GPU family in two ways:

* The size of the tree. Turing, Ampere and Ada implement 8 leaves.
  Hopper and later families implement 16.

* The write that rearms delivery. A message-signaled interrupt is
  delivered once per edge, and the PCI side delivers nothing more until
  the CPU rearms it. Before Hopper, MSI rearms by writing the
  end-of-interrupt register in the BAR0 mirror of PCI configuration
  space. On Hopper and later, MSI rearms by clearing and then setting
  the TOP enables of every serviced subtree, which produces a new edge.
  MSI-X rearms the same way on every family, but for the handler's own
  subtree only, since each subtree has its own table entry.

Add an interrupt HAL that provides the leaf count and performs the rearm
for each family. Name the interrupt type with two variants, MSI and
MSI-X, since nova-core never allocates the level-triggered INTx that the
kernel's PCI interrupt type also names.

The HAL has no user yet.

Assisted-by: LLM
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Will Pierce <wpierce@nvidia.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/20260930034148.590687-6-jhubbard@nvidia.com
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>

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