Remove a spurious closing paranthesis and tweak the comment about the
cache capacity for PTE descriptors (rmaps) eager page splitting to tone
down the assertion slightly, and to call out that topup requires dropping
mmu_lock, which is the real motivation for avoiding topup (as opposed to
memory usage).

Cc: David Matlack <dmatlack@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220712020724.1262121-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>