riscv: kvm: fix non-kernel-doc comment block

Don't use "/**" to begin a comment block for a non-kernel-doc comment.

Prevents this docs build warning:

vcpu_sbi.c:3: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 * Copyright (c) 2019 Western Digital Corporation or its affiliates.

Fixes: dea8ee31

 ("RISC-V: KVM: Add SBI v0.1 support")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Cc: Atish Patra <atish.patra@wdc.com>
Cc: Anup Patel <anup.patel@wdc.com>
Cc: kvm@vger.kernel.org
Cc: kvm-riscv@lists.infradead.org
Cc: linux-riscv@lists.infradead.org
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Message-Id: <20211107034706.30672-1-rdunlap@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>