xhci: Add payload support for control transfers logging

Print first 16 bytes of control transfer's data to debug entries.
This is helpful in debugging QMI transactions.  The current code
determines the direction (IN/OUT) using ep descriptor.  This is
correct for all endpoints except ep0.  Use URB helper functions.

Change-Id: I55b189c2f8a7dfc4636f7be830067e8c06c552ca
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>