devices/net: iter-less virtq processing pattern
devices/net: iter-less virtq processing pattern

Switched the net device code to the new virtq processing pattern,
using `virtq.pop()`, instead of `virtq.iter()`.

Signed-off-by: Dan Horobeanu <de06b8d568359df57e57b444456da06d2313ae63@amazon.com>

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