Fix all warnings caused by `clippy::cast_lossless`, which is going to be
enabled by [1].

Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/r/20250615-ptr-as-ptr-v12-5-f43b024581e8@gmail.com [1]
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250624132337.2242-2-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

FWSEC-FRTS is run with the desired address of the FRTS region as
parameter, which we need to compute depending on some hardware
parameters.

Do this in a `FbLayout` structure, that will be later extended to
describe more memory regions used to boot the GSP.

Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250619-nova-frts-v6-20-ecf41ef99252@nvidia.com
[ In doc-comment of FbLayout s/bootup process/boot process/ - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Reserve a page of system memory so sysmembar can perform a read on it if
a system write occurred since the last flush. Do this early as it can be
required to e.g. reset the GPU falcons.

Chipsets capabilities differ in that respect, so this commit also
introduces the FB HAL.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250619-nova-frts-v6-14-ecf41ef99252@nvidia.com
[ * Use kernel::page::PAGE_SIZE instead of kernel::bindings::PAGE_SIZE.
  * Get rid of the Option for SysmemFlush.
  * Slightly reword SysmemFlush doc-comments.

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