[Invisalign2] Remove duplicate logic in the following APIs

Validating the return value of btm_find_dev is not null
has been done in their callers, removing.

- SMP_PasskeyReply
- SMP_ConfirmReply
- SMP_SirkConfirmDeviceReply

Bug: 301661850
Test: atest net_test_stack
Flag: EXEMPT, no-op change
Change-Id: I88981061367640fefb42c995e44c796838e30cb0