kernel/riscv64:Added support for omatcopy on RISCV64_ZVL256B. #5648

Job	Run time
cross_build (mipsel, mipsel-linux-gnu, TARGET=MIPS1004K)	3m 32s
msys2 (UCRT64, int32, Release)	13m 26s
neoverse_build	7m 16s
cross_build (mips64el, mips64el-linux-gnuabi64, DYNAMIC_ARCH=1 TARGET=GENERIC)	3m 59s
cross_build (riscv64, riscv64-linux-gnu, TARGET=RISCV64_GENERIC)	2m 57s
cross_build (alpha, alpha-linux-gnu, TARGET=EV4)	3m 6s
msys2 (UCRT64, int32, None, mingw-w64-ucrt-x86_64, fc)	7m 58s
msys2 (UCRT64, int64, Release)	5m 56s
msys2 (MINGW32, int32, Release)	5m 58s
build (ubuntu-latest, gfortran, cmake)	4m 8s
build (ubuntu-latest, flang, cmake)	5m 55s
build (macos-latest, gfortran, cmake)	7m 6s
msys2 (CLANG64, int32, Release)	6m 7s
build (ubuntu-latest, flang, make)	4m 48s
build (ubuntu-latest, gfortran, make)	4m 51s
msys2 (CLANG64, int64, Release)	4m 36s
build (macos-latest, gfortran, make)	3m 58s
	1h 35m 37s

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