USB: xhci: Support for 64-byte contexts

Adds support for controllers that use 64-byte contexts.  The following context
data structures are affected by this: Device, Input, Input Control, Endpoint,
and Slot.  To accommodate the use of either 32 or 64-byte contexts, a Device or
Input context can only be accessed through functions which look-up and return
pointers to their contained contexts.

Signed-off-by: John Youn <johnyoun@synopsys.com>
Acked-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>