KVM: x86/mmu: Rename goal_gfn to next_last_level_gfn

KVM: x86/mmu: Rename goal_gfn to next_last_level_gfn

BugLink: https://bugs.launchpad.net/bugs/1926368
[ Upstream commit 74953d3530280dc53256054e1906f58d07bfba44 ]

The goal_gfn field in tdp_iter can be misleading as it implies that it
is the iterator's final goal. It is really a target for the lowest gfn
mapped by the leaf level SPTE the iterator will traverse towards. Change
the field's name to be more precise.

Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-13-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>