drivers: crypto: Refactor encryption and decryption functions for STM32 AES

This patch introduces a unified function pointer approach to handle
encryption and decryption operations for the STM32 AES accelerator.

- Replace separate `do_encrypt` and `do_decrypt` functions with a generic
`do_aes` function, using function pointers to AES HAL functions.

Signed-off-by: Lucas Dietrich <ld.adecy@gmail.com>