x86, kvm: cache the base of the KVM cpuid leaves

It is unnecessary to go through hypervisor_cpuid_base every time
a leaf is found (which will be every time a feature is requested
after the next patch).

Fixes: 1085ba7f552d84aa8ac0ae903fa8d0cc2ff9f79d
Cc: stable@vger.kernel.org
Cc: mtosatti@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --cc arch/x86/include/asm/kvm_para.h
Simple merge

diff --cc arch/x86/kernel/kvm.c
Simple merge