staging: android: ion: Remove check of idev->debug_root

We will go on initial idev if failed to create debug_root, and it does
not matter to check the return value of this debugfs call, just remove it.

Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>