netvsp: adding LSO validation logic to handle_rndis_packet_message

[erfrimod]

netvsp should be validating the LSO packets coming from the guest

• There should be at least two SGEs.
• The first SGE should only be the header, and therefore less than 256 bytes.

[Copilot]

Pull Request Overview

This PR adds LSO (Large Send Offload) packet validation logic to the netvsp driver's packet handling function to ensure guest-provided LSO packets meet required constraints.

Key changes:

• Adds validation for LSO packets to verify they have at least two SGEs (Scatter-Gather Elements)
• Validates that the first SGE is no larger than 256 bytes (header size constraint)
• Introduces a new error type for invalid LSO packets

[Copilot]

Using unwrap() is unsafe here even though the length check exists above. If segments is empty, this will panic. Consider using segments[0].len instead since the length check guarantees at least 2 elements, or use a safer pattern like let first_segment = &segments[0];.

Suggested change

	let first_segment_size = segments.first().unwrap().len;
	let first_segment_size = segments[0].len;

[github-actions]

At least one Petri test failed.