RISC-V: paravirt: pvqspinlock: KVM: Add paravirt qspinlock skeleton

Add the files functions needed to support the SBI PVLOCK (paravirt
qspinlock kick_cpu) extension. This is a preparation for the next
core implementation of kick_cpu.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>