xhci: Fix mult base in endpoint bandwidth info.

The "Mult" bits in the SuperSpeed Endpoint Companion Descriptor are
zero-based, and the xHCI host controller wants them to be zero-based in
the input context.  However, for the bandwidth math, we want them to be
one-based.  Fix this.

Fix the documentation about the endpoint bandwidth mult variable in the
xhci.h file, which says it is zero-based.  Also fix the documentation
about num_packets, which is also one-based, not zero-based.

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