Fix support for vector units with Zvfh #1001

Job	Run time
riscv-arch-test	0s
riscv-tests (DefaultConfig)	13m 46s
jtag-dtm-test (freechips.rocketchip.system.WithJtagDTMSystem_freechips.rocketchip.system.DefaultC...	21m 33s
riscv-tests (DefaultBufferlessConfig)	13m 47s
emulator (DefaultSmallConfig)	13m 6s
jtag-dtm-test (freechips.rocketchip.system.WithJtagDTMSystem_freechips.rocketchip.system.DefaultR...	19m 54s
riscv-tests (DefaultRV32Config)	13m 46s
jtag-dtm-test (freechips.rocketchip.system.WithJtagDTMSystem_freechips.rocketchip.system.WithDebu...	18m 38s
emulator (DualBankConfig)	13m 17s
riscv-tests (TinyConfig)	13m 18s
jtag-dtm-test (freechips.rocketchip.system.WithJtagDTMSystem_freechips.rocketchip.system.WithDebu...	17m 2s
emulator (DualChannelConfig)	13m 20s
riscv-tests (DefaultFP16Config)	13m 29s
emulator (DualChannelDualBankConfig)	13m 28s
emulator (RoccExampleConfig)	13m 14s
emulator (Edge128BitConfig)	13m 7s
emulator (Edge32BitConfig)	13m 16s
emulator (QuadChannelBenchmarkConfig)	13m 21s
emulator (EightChannelConfig)	13m 47s
emulator (DualCoreConfig)	13m 24s
emulator (MemPortOnlyConfig)	13m 4s
emulator (MMIOPortOnlyConfig)	15m 3s
emulator (CloneTileConfig)	14m 50s
emulator (HypervisorConfig)	13m 7s
	5h 34m 37s

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