bta_dm_find_services: reduce indendation

Also it's clearer now what the intention of code is.

Bug: 330675788
Bug: 335732980
Flag: com.android.bluetooth.flags.separate_service_and_device_discovery
Test: mma -j32
Change-Id: I7b11a7df3db18bea3020964ab0dbdb14b828a4ac