rust: io: add IoLoc type and generic I/O accessors

rust: io: add IoLoc type and generic I/O accessors

I/O accesses are defined by the following properties:

- An I/O location, which consists of a start address, a width, and a
  type to interpret the read value as,
- A value, which is returned for reads or provided for writes.

Introduce the `IoLoc` trait, which allows implementing types to fully
specify an I/O location.

This allows I/O operations to be made generic through the new `read` and
`write` methods.

This design will allow us to factorize the I/O code working with
primitives, and to introduce ways to perform I/O with a higher degree of
control through register types.

Co-developed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://patch.msgid.link/20260314-register-v9-5-86805b2f7e9d@nvidia.com
[ Fix incorrect reference to io_addr_assert() in try_update(). - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>