target/riscv: move 'pmp' to riscv_cpu_properties[]

target/riscv: move 'pmp' to riscv_cpu_properties[]

Move 'pmp' to riscv_cpu_properties[], creating a new setter() for it
that forbids 'pmp' to be changed in vendor CPUs, like we did with the
'mmu' option.

We'll also have to manually set 'pmp = true' to generic CPUs that were
still relying on the previous default to set it.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Tested-by: Vladimir Isaev <vladimir.isaev@syntacore.com>
Message-ID: <20240105230546.265053-6-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>