[Driver][AArch64]Add driver support for neoverse-512tvb target

The support for  neoverse-512tvb mirrors the same option available in GCC[1].
There is no functional effect for this option yet.
This patch ensures the driver accepts "-mcpu=neoverse-512tvb", and enough
plumbing is in place to allow the new option to be used in the future.

[1]https://gcc.gnu.org/onlinedocs/gcc/AArch64-Options.html

Differential Revision: https://reviews.llvm.org/D112406