Floss: Remove TARGET_FLOSS in inq_by_rssi

inq_by_rssi is controllable by sysprop, but Floss used to need
additional code because the initialization path was different.
Now looking again at the code, simplify the code to check the
sysprop directly seems to be a better option.

Bug: 345381407
Tag: #floss
Test: mmm packages/modules/Bluetooth
Flag: EXEMPT, mechanical refactor - no logical change

Change-Id: I961080f3ed6aff56166c9ecb6caa96781037800b