KVM: SVM: Account scratch allocations used to decrypt SEV guest memory

Account the temp/scratch allocation used to decrypt unaligned debug
accesses to SEV guest memory, the allocation is very much tied to the
target VM.

Reported-by: Mingwei Zhang <mizhang@google.com>
Signed-off-by: Anish Ghulati <aghulati@google.com>
Link: https://lore.kernel.org/r/20230113220923.2834699-1-aghulati@google.com


Signed-off-by: Sean Christopherson <seanjc@google.com>