Improve performance for SGEMVN on NEONVERSEN1 #5575

Job	Run time
msys2 (UCRT64, int64, Release)	15m 6s
msys2 (MINGW32, int32, Release)	14m 31s
msys2 (UCRT64, int32, None, mingw-w64-ucrt-x86_64, fc)	14m 22s
build (ubuntu-latest, gfortran, cmake)	44m 57s
build (ubuntu-latest, gfortran, make)	22m 47s
build (macos-latest, gfortran, cmake)	13m 39s
build (ubuntu-latest, flang, cmake)	43m 53s
msys2 (CLANG64, int32, Release)	1h 10m 59s
build (ubuntu-latest, flang, make)	4m 51s
build (macos-latest, gfortran, make)	3m 8s
cross_build (riscv64, riscv64-linux-gnu, TARGET=RISCV64_GENERIC)	2m 33s
cross_build (mips64el, mips64el-linux-gnuabi64, DYNAMIC_ARCH=1 TARGET=GENERIC)	3m 45s
msys2 (CLANG64, int64, Release)	1h 10m 9s
msys2 (UCRT64, int32, Release)	16m 54s
cross_build (alpha, alpha-linux-gnu, TARGET=EV4)	2m 43s
neoverse_build	8m 19s
cross_build (mipsel, mipsel-linux-gnu, TARGET=MIPS1004K)	3m 35s
	5h 56m 11s

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