Remove target_sdk_version parameter

Since linker-namespaces are enabled for all target_sdk_versions
and there is no longer need in workarounds in libnativeloader -
remove unused target_sdk_version parameter for internal calls.

This also brings libnativeloader closer to aosp/master

Bug: http://b/26040253
Change-Id: I7d6f6ac31be0dca5f3c3f6ea20e6cc87ce3a3c7f