Does PTU do statistical call traces for functions running in drivers (in the kernel)?
The answer is no. Currently the only chance to profile drivers with PTU is to use EBS profiles.
Does PTU do statistical call graphs with EBS?
On Windows - EBS so driver installation is required, however, kernel modules are not profiled.
On Linux - different technology that works on user level.
To see driver hotpots you can select some EBS profile (e.g. Profile As -> Basic Sampling).