Remove unused vars tBTM_CB::tBTM_BLE_CB::tBTM_LE_RANDOM_CB

tBTM_CB::tBTM_BLE_CB::tBTM_LE_RANDOM_CB::p
tBTM_CB::tBTM_BLE_CB::tBTM_LE_RANDOM_CB::p_generate_cback
tBTM_CB::tBTM_BLE_CB::tBTM_LE_RANDOM_CB::random_bda

Towards readable code

Bug: 163134718
Tag: #refactor
Test: acts -tc BleCocTest
Test: ble paired 2 phones

Change-Id: I8752296aef2348778fca7d9d1fa3dce67017cee2