target/riscv/tcg: use isa_edata_arr[] in riscv_cpu_update_misa_x()

The non-standard extensions, in this particular function the vendor extensions, are all riscv,isa names that starts with 'x'. In theory this is a bit slower than using riscv_cpu_vendor_exts (isa_edata_arr is longer) but riscv_cpu_update_misa_x() is executed only once during finalize(), i.e. not a hot path. We're accepting a tiny performance hit as as a tradeoff for the code simplication we'll have later by removing all riscv_cpu_* arrays. Signed-off-by: Daniel Henrique Barboza <daniel.barboza@oss.qualcomm.com> Acked-by: Alistair Francis <alistair.francis@wdc.com> Message-ID: <20260512032926.1978818-9-daniel.barboza@oss.qualcomm.com> Signed-off-by: Alistair Francis <alistair.francis@wdc.com>