Fix support for vector units with Zvfh #1002

Job	Run time
jtag-dtm-test (freechips.rocketchip.system.WithJtagDTMSystem_freechips.rocketchip.system.DefaultC...	21m 39s
riscv-arch-test	0s
jtag-dtm-test (freechips.rocketchip.system.WithJtagDTMSystem_freechips.rocketchip.system.DefaultR...	19m 57s
riscv-tests (DefaultConfig)	19m 20s
emulator (DefaultSmallConfig)	12m 50s
jtag-dtm-test (freechips.rocketchip.system.WithJtagDTMSystem_freechips.rocketchip.system.WithDebu...	18m 4s
riscv-tests (DefaultBufferlessConfig)	19m 35s
emulator (DualBankConfig)	13m 22s
jtag-dtm-test (freechips.rocketchip.system.WithJtagDTMSystem_freechips.rocketchip.system.WithDebu...	17m 17s
riscv-tests (DefaultRV32Config)	18m 28s
emulator (DualChannelConfig)	13m 11s
riscv-tests (TinyConfig)	13m 35s
emulator (DualChannelDualBankConfig)	13m 43s
riscv-tests (DefaultFP16Config)	14m 4s
emulator (RoccExampleConfig)	13m 17s
emulator (Edge128BitConfig)	13m 13s
emulator (Edge32BitConfig)	12m 57s
emulator (QuadChannelBenchmarkConfig)	13m 39s
emulator (EightChannelConfig)	13m 37s
emulator (DualCoreConfig)	14m 3s
emulator (MemPortOnlyConfig)	13m 27s
emulator (MMIOPortOnlyConfig)	13m 2s
emulator (CloneTileConfig)	14m 50s
emulator (HypervisorConfig)	13m 9s
	5h 50m 19s

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