drm/amdgpu: Apply retry to IP discovery v2 and v4

To ensure GPU driver touch the local framebuffer until
it is initialized by integrated firmware.

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Likun Gao <Likun.Gao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>