[sw/sca] Refactor common sca code in preparation for a new library
[sw/sca] Refactor common sca code in preparation for a new library

This change refactors some device init and handling code that is
expected to be shared between different SCA targets:
- Initialization of pinmux, UART, GPIO, and timer,
- IRQ handling,
- Trigger handling, and
- Sleeping during encryption operations.

Signed-off-by: Alphan Ulusoy <23b245cc5a07aacf75a9db847b24c67dee1707bf@google.com>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan