Implement the array_size() function in the LinuxKPI. This function
basically multiplies its two arguments and returns SIZE_MAX if the
result overflows the size_t type. Else the product of the two
arguments is returned.

Bump the FreeBSD_version to mitigate issues with existing
implementation of array_size() in drm-devel-kmod.

Discussed with: manu@
MFC after: 1 week
Sponsored by: Mellanox Technologies