Remove dependency on libsoftkeymaster.

This is part of a refactor to facilitate reuse in Keymaster 4.1 VTS
tests.

Bug: 140193672
Bug: 140192237
Test: VtsHalKeymasterV4_0TargetTest
Change-Id: I9310a851648c028850f9795d303419c6a7e29a11
Merged-In: I9310a851648c028850f9795d303419c6a7e29a11