drm/amdgpu: return error when eeprom checksum failed

Return eeprom table checksum error result, otherwise
it might be overwritten by next call.

V2: replace DRM_ERROR with dev_err

Signed-off-by: Jinzhou Su <jinzhou.su@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>