KVM: arm64: account pKVM reclaim against the VM mm

KVM: arm64: account pKVM reclaim against the VM mm

Protected guest faults charge long term pins to the VM's mm. Teardown
can run later from file release, where current->mm may be unrelated.

Drop the charge from kvm->mm instead.

Fixes: 4e6e03f9eadd ("KVM: arm64: Hook up reclaim hypercall to pkvm_pgtable_stage2_destroy()")
Signed-off-by: Bradley Morgan <include@grrlz.net>
Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>
Tested-by: Fuad Tabba <fuad.tabba@linux.dev>
Link: https://patch.msgid.link/20260621213155.6019-1-include@grrlz.net
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org