The DRM generic code started to import this header directly in Linux 6.12.x. Let's move the definition of ARRAY_SIZE() (the only thing that <linux/array_size.h> defines) to this header.
Also, include <linux/array_size.h> from the same headers as Linux. This includes <linux/kernel.h>, so the change should not break anything.
This is part of the update of DRM drivers to Linux 6.12.81.
Sponsored by: The FreeBSD Foundation