opencl : fix memory allocation size

[sparkleholic]

issue:
CodeLinaro#17 (comment)

This patch fixes the memory allocation size
not exceeding the maximum size of the OpenCL device.

[sparkleholic]

@lhez, @bandoti <

Please take a look at this patch. I think it could help address the issue where the existing code exceeds MAX_MEM_ALLOC_SIZE during memory allocation. It might serve as a temporary solution until we come up with a more refined fix. What do you think?

[sparkleholic]

@lhez is not responding to my request. @max-krasnyansky, Could you review this PR?
Current implementation might cause runtime error while calling clCreateBuffer with the size exceeding the OpenCL device's maximum memory allocation size.
This patch prevents this bug.

[max-krasnyansky]

Yep. Looks good to me (i.e. better than the original version).

@lhez we should add some comments about how those A_q_*_bytes magic numbers were computed.

[lhez]

Yeah, we need to add some comments. Did some calculation last night and I think I recalled the calculation. I think we should make the calculation more formal and print out limitations when allocation is limited.