drm: add tests/amdgpu (v3)

This adds some basic unit tests for the new amdgpu driver.

v2: use common util_math.h
v3: implement suggestions from Emil
    replace malloc/memset with calloc
    make header guards all caps
    use posix_memalign rather than mem_align
    replace malloc with calloc for pm4 allocations
    make CU_SuiteInfo static
    fix Makefile.am
    fix fd numbering
    use drmGetVersion/drmFreeVersion rather than open coding it
    close fd, clean up CU registry on error

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>