vmm_vhost: eliminate unnecessary collect() into a Vec
vmm_vhost: eliminate unnecessary collect() into a Vec

The `buf_lens` vector was created only to be destroyed in the next line.
Just use `sum()` on the buf iterator.

BUG=None
TEST=tools/presubmit --all

Change-Id: Iddfa4f783b6eda326b9dbb9c6a1f443b7976ca2c
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3858688
Reviewed-by: Keiichi Watanabe <815e4e8f7c92a23424d7c3f51ead622bcedbc720@chromium.org>
Commit-Queue: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Auto-Submit: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Tested-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm