Remove return value stack/btm/btm_ble_gap::btm_ble_start_scan am: b616445f...

Remove return value stack/btm/btm_ble_gap::btm_ble_start_scan am: b616445f am: 421b1176 am: 1e2a67be

Original change: https://android-review.googlesource.com/c/platform/system/bt/+/1488201

Change-Id: I0d842190a83aed1d78bd7f5d562837d7d49a6d02