KVM: arm64: nvhe: Fix a non-kernel-doc comment

Do not use kernel-doc "/**" notation when the comment is not in
kernel-doc format.

Fixes this docs build warning:

arch/arm64/kvm/hyp/nvhe/sys_regs.c:478: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
    * Handler for protected VM restricted exceptions.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Cc: Fuad Tabba <tabba@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: kvmarm@lists.cs.columbia.edu
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211106032529.15057-1-rdunlap@infradead.org