drm_hwcomposer: avoid using signed errno on uint32 type
DrmGenericImporter::ConvertHalFormatToDrm() should not return negative values. - Use DRM_FORMAT_INVALID instead of -EINVAL - Check DrmGenericImporter::ConvertHalFormatToDrm() result value in DrmGenericImporter::ImportBuffer() Signed-off-by: Roman Stratiienko <roman.stratiienko@globallogic.com>