tc: B.W limits can now be specified in %.

tc: B.W limits can now be specified in %.

This patch adapts the tc command line interface to allow bandwidth limits
to be specified as a percentage of the interface's capacity.

Adding this functionality requires passing the specified device string to
each class/qdisc which changes the prototype for a couple of functions: the
.parse_qopt and .parse_copt interfaces. The device string is a required
parameter for tc-qdisc and tc-class, and when not specified, the kernel
returns ENODEV. In this patch, if the user tries to specify a bandwidth
percentage without naming the device, we return an error from userspace.

Signed-off-by: Nishanth Devarajan<ndev2021@gmail.com>