Comment # 25 on bug 1175908 from Takashi Iwai

The driver module got dropped in the recent upstream, commit
1d2c3279311e4f03fcf164e1366f2fda9f4bfccf
    crypto: x86/aes - drop scalar assembler implementations

    The AES assembler code for x86 isn't actually faster than code
    generated by the compiler from aes_generic.c, and considering
    the disproportionate maintenance burden of assembler code on
    x86, it is better just to drop it entirely. Modern x86 systems
    will use AES-NI anyway, and given that the modules being removed
    have a dependency on aes_generic already, we can remove them
    without running the risk of regressions.

So this sounds like the missing aes_generic in initrd?