[USBSTOR] CORE-19773 Clamp LUN - Don't just assert on a POSSIBLE case

[anonymou0719]

This PR ports a small fix from DarkFire01/reactos into ReactOS-Longhorn-Initiative/reactos.

We’re a team doing OSS research, and part of our work is helping useful fixes move across forks so different trees stay aligned and don’t drift too much over time.

Ported commit: http://github.com/DarkFire01/reactos/commit/c344fd3df4d43d772a186907f67adda02c5f4c2c
(Original source reference mentioned in the upstream notes: http://github.com/DarkFire01/reactos/commit/2d79555179c3ade2f5e6ee6650fb68b69e29a7cd)

What changed (kept small and easy to review):

• Only one file is updated: drivers/usb/usbstor/scsi.c
• No refactors, cleanup, or formatting-only changes mixed in

Why this is useful:

• Fixes an issue in the USB storage (usbstor) SCSI handling code
• Helps keep the Longhorn Initiative fork consistent with fixes already present in DarkFire01/reactos

Testing:

• Local testing: not included yet (feel free to replace this with the exact build/test commands you ran)
• CI link: N/A

If you’d prefer this rebased, squashed, or applied to a different branch, I’m happy to adjust.