Fix crash in btm_ble_gap

Changes to native PHY handling  introduced a memory safety issue when
multiple PHY are requested.  Fix that.

Note: we plan to make additional changes to PHY handling on AOSP to
address further deficiencies with the implementation.  Those are however
not security vulnerabilities and do not need backporting.

Bug: 333347572
Test: m libbluetooth
Ignore-AOSP-First: security
Tag: security
Flag: com.android.bluetooth.flags.phy_to_native
Change-Id: I1379b0f76565ccac3c1fe2a2e2dd9564e09c7678