KVM: x86/mmu: Rename 'hlevel' to 'level' in FNAME(fetch)

Rename 'hlevel', which presumably stands for 'host level', to simply
'level' in FNAME(fetch).  The variable hasn't tracked the host level for
quite some time.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200923183735.584-7-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>