gpu: nova-core: wait for GFW_BOOT completion

Upon reset, the GPU executes the GFW (GPU Firmware) in order to
initialize its base parameters such as clocks. The driver must ensure
that this step is completed before using the hardware.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250619-nova-frts-v6-12-ecf41ef99252@nvidia.com


[ Slightly adjust comments in wait_gfw_boot_completion(). - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>