USB: xhci: Make endpoint interval debugging clearer.

The xHCI hardware can only handle polling intervals that are a power of
two.  When we add a new endpoint during a bandwidth allocation, and the
polling interval is rounded down to a power of two, print the original
polling interval in the endpoint descriptor.

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