runtime,cmd/compile: change reg duff{zero,copy} for regabi riscv64

runtime,cmd/compile: change reg duff{zero,copy} for regabi riscv64

As CL 356519 require, X8-X23 will be argument register, however X10, X11
is used by duff device.

This CL changes X10, X11 into X24, X25 to meet the prerequisite.

Update #40724

Change-Id: Ie9b899afbba7e9a51bb7dacd89e49ca1c1fc33ff
Reviewed-on: https://go-review.googlesource.com/c/go/+/357976
Trust: mzh <mzh@golangcn.org>
Run-TryBot: mzh <mzh@golangcn.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Joel Sing <joel@sing.id.au>