Simplify two vcreate macros in helperrvv.h #244

Job	Run time
build-native-gcc	3m 34s
build-native-llvm	3m 49s
test-native-gcc	9m 46s
build-aarch64-gcc	10m 8s
test-native-llvm	7m 28s
build-aarch64-llvm	8m 24s
build-armhf-gcc	6m 18s
build-armhf-llvm	3m 31s
build-ppc64el-gcc	9m 8s
build-ppc64el-llvm	8m 18s
build-s390x-gcc	7m 7s
build-s390x-llvm	4m 23s
build-riscv64-llvm	4m 48s
test-aarch64-gcc (qemu_cpu: "max,sve=off")	20m 27s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve128=on")	22m 29s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve256=on")	25m 32s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve512=on")	33m 24s
test-aarch64-llvm (qemu_cpu: "max,sve=off")	18m 57s
test-aarch64-llvm (qemu_cpu: "max,sve=on,sve128=on")	23m 32s
test-aarch64-llvm (qemu_cpu: "max,sve=on,sve256=on")	26m 41s
test-aarch64-llvm (qemu_cpu: "max,sve=on,sve512=on")	32m 32s
test-armhf-gcc (qemu_cpu: "max")	16m 55s
test-armhf-llvm (qemu_cpu: "max")	16m 26s
test-ppc64el-gcc (qemu_cpu: "power10")	30m 27s
test-ppc64el-llvm (qemu_cpu: "power10")	25m 14s
test-s390x-gcc (qemu_cpu: "")	23m 21s
test-s390x-llvm (qemu_cpu: "")	21m 26s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=false")	6m 2s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=128,elen=64,vext_spec=v1.0")	16m 51s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=256,elen=64,vext_spec=v1.0")	23m 13s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=512,elen=64,vext_spec=v1.0")	33m 44s
	8h 23m 55s

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