KVM: selftests: Add vcpu_set_cpuid_property() to set properties

KVM: selftests: Add vcpu_set_cpuid_property() to set properties

Add vcpu_set_cpuid_property() helper function for setting properties, and
use it instead of open coding an equivalent for MAX_PHY_ADDR.  Future vPMU
testcases will also need to stuff various CPUID properties.

Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-13-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>