gpu: nova-core: Add code comments related to devinit

Add several code comments to reduce acronym soup and explain how devinit
magic and bootflow works before driver loads. These are essential for
debug and development of the nova driver.

[acourbot@nvidia.com: reformat and reword a couple of sentences]

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250708-nova-docs-v4-1-9d188772c4c7@nvidia.com


Signed-off-by: Danilo Krummrich <dakr@kernel.org>