system/common: Remove location parameter from MessageLoopThread

This change was already applied to do_in_jni_thread and
do_in_main_thread. Removing the parameter from MessageLoopThread
will bring the API closed to os::Handler.

Bug: 331817295
Test: m com.android.bt
Flag: EXEMPT, no logical change
Change-Id: Iaadaf638de318acba695a49ebe51b69edbd12e0b