[AArch64][NFC] Drop 'V' from ASIMD FP convert, other, D/Q-form regex

In the Cortex A57 Optimization Guide [1] VCVTAU (AArch32) is incorrectly
listed in the AArch64 instructions for instruction groups:

  - ASIMD FP convert, other, D-form
  - ASIMD FP convert, other, Q-form

It's meant to be FCVTAU, this will be fixed in future releases of the guide.

[1] https://developer.arm.com/documentation/uan0015/b