target/riscv/tcg: update priv_ver on user_set extensions

target/riscv/tcg: update priv_ver on user_set extensions

We'll add a new bare CPU type that won't have any default priv_ver. This
means that the CPU will default to priv_ver = 0, i.e. 1.10.0.

At the same we'll allow these CPUs to enable extensions at will, but
then, if the extension has a priv_ver newer than 1.10, we'll end up
disabling it. Users will then need to manually set priv_ver to something
other than 1.10 to enable the extensions they want, which is not ideal.

Change the setter() of extensions to allow user enabled extensions to
bump the priv_ver of the CPU. This will make it convenient for users to
enable extensions for CPUs that doesn't set a default priv_ver.

This change does not affect any existing CPU: vendor CPUs does not allow
extensions to be enabled, and generic CPUs are already set to priv_ver
LATEST.

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: <20231218125334.37184-4-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>