Performance improvements of [SD]DOT with loop-unrolling on A64FX #5860

Job	Run time
msys2 (UCRT64, int32, Release)	14m 16s
neoverse_build	7m 59s
msys2 (CLANG64, int64, Release)	1h 9m 47s
msys2 (MINGW32, int32, Release)	15m 47s
build (ubuntu-latest, flang, make)	17m 31s
build (macos-latest, gfortran, cmake)	12m 37s
build (ubuntu-latest, gfortran, make)	22m 1s
msys2 (CLANG64, int32, Release)	1h 11m 16s
msys2 (UCRT64, int32, None, mingw-w64-ucrt-x86_64, fc)	11m 49s
build (macos-latest, gfortran, make)	9m 9s
build (ubuntu-latest, flang, cmake)	44m 57s
build (ubuntu-latest, gfortran, cmake)	45m 26s
msys2 (UCRT64, int64, Release)	1h 42m 7s
cross_build (riscv64, riscv64-linux-gnu, TARGET=RISCV64_GENERIC)	2m 52s
cross_build (mipsel, mipsel-linux-gnu, TARGET=MIPS1004K)	3m 27s
cross_build (mips64el, mips64el-linux-gnuabi64, DYNAMIC_ARCH=1 TARGET=GENERIC)	3m 31s
cross_build (alpha, alpha-linux-gnu, TARGET=EV4)	2m 53s
	7h 37m 25s

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