KVM/x86: pmu: Fix #GP condition check for RDPMC emulation

In guest protected mode, if the current privilege level
is not 0 and the PCE flag in the CR4 register is cleared,
we will inject a #GP for RDPMC usage.

Signed-off-by: Like Xu <like.xu@linux.intel.com>
Message-Id: <20200708074409.39028-1-like.xu@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>