[CUDA] Fix result of CL_DEVICE_MEM_BASE_ADDR_ALIGN query
[CUDA] Fix result of CL_DEVICE_MEM_BASE_ADDR_ALIGN query

The CUDA programming guide states that all memory allocations are
aligned to at least 256 bytes.

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