RISC-V: KVM: Correct kvm_riscv_check_vcpu_requests() comment

Correct `check_vcpu_requests` to `kvm_riscv_check_vcpu_requests` in
comments.

Fixes: f55ffaf8 ("RISC-V: KVM: Enable ring-based dirty memory tracking")
Signed-off-by: Quan Zhou <zhouquan@iscas.ac.cn>
Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/49680363098c45516ec4b305283d662d26fa9386.1754326285.git.zhouquan@iscas.ac.cn


Signed-off-by: Anup Patel <anup@brainfault.org>