vmm: Init PMU for vcpu when create vm

PMU is needed in guest for performance profiling, thus should be
enabled.

Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>

arch/src/aarch64/mod.rs

@@ -43,6 +43,9 @@ pub enum Error {
 
     /// Error configuring the MPIDR register
     VcpuRegMpidr(hypervisor::HypervisorCpuError),
+
+    /// Error initializing PMU for vcpu
+    VcpuInitPmu,
 }
 
 impl From<Error> for super::Error {