[RISCV] Remove some instructions from Zvfbfwma by implying Zfbfmin according to the latest spec

According to the latest spec, Zvfbfwma requires Zvfbfmin and Zvfbfmin requires Zfbfmin, with FLH/FSH/FMV.H.X/HMV.X.H removed from Zvfbfwma.

Reviewed By: asb

Differential Revision: https://reviews.llvm.org/D155916