[sw, sca] Rename aes_serial_encrypt() function for disambiguation
[sw, sca] Rename aes_serial_encrypt() function for disambiguation

This is the underlying function called by several simple serial commands
but it is itself not a simple serial command.

Signed-off-by: Pirmin Vogel <386a7fc8e7338ed7899b4d9883c0ebec5de81366@lowrisc.org>

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