platform/x86: mlx-platform: Move module from arch/x86

Since mlx-platform is not an architectural driver, it is moved out
of arch/x86/platform to drivers/platform/x86.
Relevant Makefile and Kconfig are updated.

Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index 3e30399..960f364f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7879,7 +7879,7 @@
 M:      Vadim Pasternak <vadimp@mellanox.com>
 L:      platform-driver-x86@vger.kernel.org
 S:      Supported
-F:      arch/x86/platform/mellanox/mlx-platform.c
+F:      drivers/platform/x86/mlx-platform.c
 
 MELLANOX MLX CPLD HOTPLUG DRIVER
 M:	Vadim Pasternak <vadimp@mellanox.com>