sys_util: net: Make clippy clean
sys_util: net: Make clippy clean

Use from instead of as.

Signed-off-by: Dylan Reid <c791bfe44996c1eed9c7149a0c5f12a86d58eb85@chromium.org>
Change-Id: I02342bd352cd98417011ceb5a79ba5bde5551a07
Reviewed-on: https://chromium-review.googlesource.com/1510071
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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