target/riscv: Promote svade to a normal extension

target/riscv: Promote svade to a normal extension

Named features are extensions which don't make sense for users to
control and are therefore not exposed on the command line. However,
svade is an extension which makes sense for users to control, so treat
it like a "normal" extension. The default is false, even for the max
cpu type, since QEMU has always implemented hardware A/D PTE bit
updating, so users must opt into svade (or get it from a CPU type
which enables it by default).

Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240215223955.969568-7-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>