iommu/arm-smmu: fix incorrect comment regarding TLB invalidation

Commit 1463fe44fd0f ("iommu/arm-smmu: Don't use VMIDs for stage-1
translations") moved our TLB invalidation from context creation time to
context destruction time, but forgot to update an associated comment.

This patch fixes the broken comment.

Change-Id: Id4d0266207510055727263886294addc0ebe7676
Signed-off-by: Will Deacon <will.deacon@arm.com>
Git-commit: 34fb4b37b7b6da7dc34797d1abf234dd30b091d8
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>