Corrected USB Control Request Type definitions

Even though they are not being used, might as well set them right. The other option would be to delete these four lines. For reference, http://www.beyondlogic.org/usbnutshell/usb6.shtml

SIgned-off-by Venkatesh Shukla <venkatesh.shukla.eee11@iitbhu.ac.in>
Merge pull request #63 from venkateshshukla/patch-1

Corrected USB Control Request Type definitions