Simplify two vcreate macros in helperrvv.h #246

Job	Run time
build-native-gcc	5m 43s
build-native-llvm	4m 18s
test-native-gcc	7m 46s
build-aarch64-gcc	3m 58s
test-native-llvm	9m 43s
build-aarch64-llvm	2m 59s
build-armhf-gcc	4m 12s
build-armhf-llvm	1m 40s
build-ppc64el-gcc	2m 50s
build-ppc64el-llvm	3m 47s
build-s390x-gcc	5m 58s
build-s390x-llvm	2m 37s
build-riscv64-llvm	4m 15s
test-aarch64-gcc (qemu_cpu: "max,sve=off")	18m 16s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve128=on")	24m 44s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve256=on")	27m 3s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve512=on")	33m 49s
test-aarch64-llvm (qemu_cpu: "max,sve=off")	16m 16s
test-aarch64-llvm (qemu_cpu: "max,sve=on,sve128=on")	21m 47s
test-aarch64-llvm (qemu_cpu: "max,sve=on,sve256=on")	29m 22s
test-aarch64-llvm (qemu_cpu: "max,sve=on,sve512=on")	29m 20s
test-armhf-gcc (qemu_cpu: "max")	15m 26s
test-armhf-llvm (qemu_cpu: "max")	16m 22s
test-ppc64el-gcc (qemu_cpu: "power10")	28m 5s
test-ppc64el-llvm (qemu_cpu: "power10")	28m 5s
test-s390x-gcc (qemu_cpu: "")	19m 18s
test-s390x-llvm (qemu_cpu: "")	18m 46s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=false")	7m 23s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=128,elen=64,vext_spec=v1.0")	15m 38s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=256,elen=64,vext_spec=v1.0")	22m 6s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=512,elen=64,vext_spec=v1.0")	33m 57s
	7h 45m 29s

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