mellanox: Relocate mlx-platform driver

Move 'mlx-platform' driver 'x86' to 'mellanox' folder.

Motivation to allow running it on systems with ARM architecture.

Since drivers/platform/x86/mlx-platform.c is rellocated to folder
drivers/platform/x86/, remove "MELLANOX PLATFORM DRIVER" item.
This driver will be located under "MELLANOX HARDWARE PLATFORM SUPPORT"
item.

Reviewed-by: Michael Shych <michaelsh@nvidia.com>
Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
Link: https://lore.kernel.org/r/20250124172632.22437-2-vadimp@nvidia.com


Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>