Simplify definition of fallback vendor ID
Simplify definition of fallback vendor ID

The reported value currently remains the same, but should be replaced by
the appropriate value registered with Khronos.

franz/pocl,pocl/pocl,Oblomov/pocl,franz/pocl,franz/pocl,Oblomov/pocl,pocl/pocl,franz/pocl,pocl/pocl,pocl/pocl,Oblomov/pocl,franz/pocl,Oblomov/pocl,pocl/pocl,Oblomov/pocl