gpu: nova-core: register: minor grammar and spelling fixes

gpu: nova-core: register: minor grammar and spelling fixes

There is only one top-level macro in this file at the moment, but the
"macros.rs" file name allows for more. Change the wording so that it
will remain valid even if additional macros are added to the file.

Fix a couple of spelling errors and grammatical errors, and break up a
run-on sentence, for clarity.

Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://lore.kernel.org/r/20250718-nova-regs-v2-1-7b6a762aa1cd@nvidia.com
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>