Use HSA_AMD_AGENT_INFO_COOPERATIVE_COMPUTE_UNIT_COUNT to get compute
units. This is needed to work around assymentric CU harvesting bug on
gfx90a. Add a new device property to get the max available CUs on the
device.
Change-Id: I878f38f14f16c1af01fc0a77157aea1e816a63b8
[ROCm/clr commit: 33aca5a4a6]