target/riscv: add riscv,isa to named features

target/riscv: add riscv,isa to named features

Further discussions after the introduction of rva22 support in QEMU
revealed that what we've been calling 'named features' are actually
regular extensions, with their respective riscv,isa DTs. This is
clarified in [1]. [2] is a bug tracker asking for the profile spec to be
less cryptic about it.

As far as QEMU goes we understand extensions as something that the user
can enable/disable in the command line. This isn't the case for named
features, so we'll have to reach a middle ground.

We'll keep our existing nomenclature 'named features' to refer to any
extension that the user can't control in the command line. We'll also do
the following:

- 'svade' and 'zic64b' flags are renamed to 'ext_svade' and
  'ext_zic64b'. 'ext_svade' and 'ext_zic64b' now have riscv,isa strings and
  priv_spec versions;

- skip name feature check in cpu_bump_multi_ext_priv_ver(). Now that
  named features have a riscv,isa and an entry in isa_edata_arr[] we
  don't need to gate the call to cpu_cfg_ext_get_min_version() anymore.

[1] https://github.com/riscv/riscv-profiles/issues/121
[2] https://github.com/riscv/riscv-profiles/issues/142

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240215223955.969568-3-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>