RISC-V: KVM: Sort ISA extensions alphabetically in ONE_REG interface

Let us sort isa extensions alphabetically in kvm_isa_ext_arr[] and
kvm_riscv_vcpu_isa_disable_allowed() so that future insertions are
more predictable.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Anup Patel <anup@brainfault.org>