drm/amdgpu: Change VRAM lost print from ERR to INF

It's normal for VRAM to lost during GPU reset and so change
the log level to INFO to avoid confusing users.

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>