linux-user/strace.list: add riscv_hwprobe entry

linux-user/strace.list: add riscv_hwprobe entry

We're missing a strace entry for riscv_hwprobe, and using -strace will
report it as "Unknown syscall 258".

After this patch we'll have:

$ ./build/qemu-riscv64 -strace test_mutex_riscv
110182 riscv_hwprobe(0x7f207efdc700,1,0,0,0,0) = 0
110182 brk(NULL) = 0x0000000000082000
(...)

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20250728170633.113384-1-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>