tests/amdgpu: ensure tests work by using c99 initializers

In the latest version of CUnit the fourth parameter of the CU_SuiteInfo
struct is pSetUpFunc rather than *pTests.

Seems like the CUnit ABI broke at some point, so let's the the robust
thing and use c99 designated initializers to correctly populate the
struct(s).

Cc: Leo Liu <leo.liu@amd.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>