[AArch64] Add Fujitsu A64FX scheduling model
Basic support of A64FX was added in D75594 but its scheduling model
was missing. This commit adds the scheduling model. Also, this commit
amends/adds some subtarget parameters of A64FX.
The A64FX Microarchitecture Manual, which is source information of
this commit, is on GitHub.
Differential Revision: https://reviews.llvm.org/D93791