gpu: nova-core: add the GIN vector, leaf and subtree types

GIN, the GPU Interrupt and Notification unit, is the GPU's interrupt
controller. Each interrupt source has a GIN vector number, and the
controller latches a pending vector in a two-level tree: one bit of a
LEAF register, summarized two leaves at a time by one bit of the TOP
register. A vector's number fixes its position in that tree:

    leaf    = vector / 32
    bit     = vector % 32
    subtree = leaf / 2

A tree implements either 8 or 16 leaves, depending on the GPU family.
The leaf count sets both the number of subtrees and the highest vector
that the tree carries.

Without distinct types, a vector, a leaf index, a set of vectors within
one leaf, a subtree and a set of subtrees are all plain integers. A
caller can pass one where another belongs, and a register field can
accept the wrong one.

Add a type for each of those, and for the leaf count. A vector converts
to its own leaf, bit and subtree. Its constructor rejects, at build
time, a number beyond the widest supported tree, and a validation
method rejects, at run time, a number beyond the leaves that the
current tree implements. A leaf count yields the set of subtrees that
it implements.

The module has no user yet.

Suggested-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/20260930034148.590687-4-jhubbard@nvidia.com
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>

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