Issue Description

When connected to a USB2.1 port one cannot set the depth exposure time shorter than 70usec.
Exp times shorter than 70usec will lead to artifacts and over-exposed frames.

Steps to Reproduce

• Connect a D435 to a USB 2.1 port and open realsense-viewer
• Enable infra1 stream and set "enable auto exposure" to OFF
• Set exposure time to something like 100usec and you get unaffected frames
• Set exposure time to any value lower than 70usec and the frame becomes over-exposed (it looks brighter than at 100usec) and will show artifacts.

ATTENTION: When using a USB3.2 port we could not observe this issue

USB2.1, 90usec exposure	USB3.2, 90usec exposure

USB2.1, 60usec exposure	USB3.2, 60usec exposure

USB2.1, 1usec exposure, artifacts (salt and pepper)