x86/hvm: vmx/svm_cpu_up_prepare should be called only once

x86/hvm: vmx/svm_cpu_up_prepare should be called only once

These routines are first called via CPU_UP_PREPARE notifier by
the BSP and then by the booting ASP from vmx_cpu_up()/_svm_cpu_up().

Avoid the unnecessary second call. Because BSP doesn't go through
CPU_UP_PREPARE it is a special case. We pass 'bsp' flag to newly
added _vmx_cpu_up() (just like it's already done for _svm_cpu_up())
so they can decide whether or not to call vmx/svm_cpu_up_prepare().

Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>