### Description There are two ibex drivers: - [silicon_creator driver](https://github.com/lowRISC/opentitan/blob/master/sw/device/silicon_creator/lib/drivers/ibex.h) - [cryptolib driver](https://github.com/lowRISC/opentitan/blob/master/sw/device/lib/crypto/drivers/rv_core_ibex.h) Also the silicon_creator has a [rnd driver](https://github.com/lowRISC/opentitan/blob/master/sw/device/silicon_creator/lib/drivers/rnd.h). The following items (at least) should be looked at: - [ ] [`ibex_rnd32_read`](https://github.com/lowRISC/opentitan/blob/master/sw/device/lib/crypto/drivers/rv_core_ibex.h#L55): move to silicon_creator - [ ] [`ibex_{enable,disable}_icache`](https://github.com/lowRISC/opentitan/blob/master/sw/device/lib/crypto/drivers/rv_core_ibex.h#L24): move to silicon_creator - [ ] [`ibex_check_security_config`](https://github.com/lowRISC/opentitan/blob/master/sw/device/lib/crypto/drivers/rv_core_ibex.h#L45): keep in cryptolib - [ ] [`ibex_clear_rf`](https://github.com/lowRISC/opentitan/blob/master/sw/device/lib/crypto/drivers/rv_core_ibex.h#L70): keep in cryptolib - [ ] create `ibex` mock - [ ] expand `ibex` unittest - [ ] maybe turn [the cryptolib rv_core_ibex mock into a real mock](https://github.com/lowRISC/opentitan/blob/master/sw/device/lib/crypto/drivers/mock_rv_core_ibex.cc)