Improve performance for SGEMVN on NEONVERSEN1 #5572

Job	Run time
cross_build (mips64el, mips64el-linux-gnuabi64, DYNAMIC_ARCH=1 TARGET=GENERIC)	3m 45s
neoverse_build	8m 58s
cross_build (riscv64, riscv64-linux-gnu, TARGET=RISCV64_GENERIC)	2m 38s
cross_build (mipsel, mipsel-linux-gnu, TARGET=MIPS1004K)	3m 40s
msys2 (CLANG64, int64, Release)	1h 15m 26s
cross_build (alpha, alpha-linux-gnu, TARGET=EV4)	2m 48s
msys2 (MINGW32, int32, Release)	18m 28s
msys2 (UCRT64, int32, None, mingw-w64-ucrt-x86_64, fc)	11m 54s
msys2 (UCRT64, int64, Release)	14m 28s
msys2 (CLANG64, int32, Release)	1h 8m 32s
msys2 (UCRT64, int32, Release)	12m 57s
build (macos-latest, gfortran, cmake)	11m 32s
build (ubuntu-latest, flang, cmake)	10m 25s
build (ubuntu-latest, flang, make)	17m 30s
build (ubuntu-latest, gfortran, cmake)	44m 41s
build (ubuntu-latest, gfortran, make)	21m 13s
build (macos-latest, gfortran, make)	3m 5s
	5h 32m 0s

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