Remove warning from VNDK's <cutils/log.h>

We're never going to fix this warning and it's not causing any active
issues that vendors are using this header.  It is however causing
active issues that we have extraneous warning messages in the log.

Bug: 123758136
Test: no build warnings from <cutils/log.h>
Change-Id: Iccf702bf2536ba106a00ac04467d54401cbe2a50