drm/amdgpu: Prefer default discovery offset

drm/amdgpu: Prefer default discovery offset

If a valid signature is seen at the default offset, use the default
size/offset for discovery.

Fixes: 01bdc7e219c4 ("drm/amdgpu: New interface to get IP discovery binary v3")
Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/5447
Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 46a0df99a0b2fa2fa61d864b04b6a5d5fe748779)
Cc: stable@vger.kernel.org