aes: Move the AES-128-CBC encryption function to common code

Move the AES-128-CBC encryption function implemented in
tegra20-common/crypto.c into lib/aes.c . This is well re-usable common
code. Moreover, clean the code up a bit and fix the kerneldoc-style
annotations.

Signed-off-by: Marek Vasut <marex@denx.de>