Improve performance for SGEMVN on NEONVERSEN1 #5576

Job	Run time
msys2 (UCRT64, int64, Release)	14m 45s
msys2 (UCRT64, int32, Release)	17m 3s
cross_build (mips64el, mips64el-linux-gnuabi64, DYNAMIC_ARCH=1 TARGET=GENERIC)	3m 33s
msys2 (MINGW32, int32, Release)	16m 39s
cross_build (riscv64, riscv64-linux-gnu, TARGET=RISCV64_GENERIC)	2m 35s
msys2 (CLANG64, int32, Release)	19m 34s
build (ubuntu-latest, flang, cmake)	10m 33s
neoverse_build	7m 48s
cross_build (alpha, alpha-linux-gnu, TARGET=EV4)	2m 36s
build (ubuntu-latest, gfortran, cmake)	44m 44s
cross_build (mipsel, mipsel-linux-gnu, TARGET=MIPS1004K)	3m 19s
msys2 (CLANG64, int64, Release)	18m 28s
msys2 (UCRT64, int32, None, mingw-w64-ucrt-x86_64, fc)	13m 54s
build (macos-latest, gfortran, make)	3m 10s
build (ubuntu-latest, gfortran, make)	21m 9s
build (ubuntu-latest, flang, make)	4m 47s
build (macos-latest, gfortran, cmake)	13m 14s
	3h 37m 51s

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