drm/amdkfd: Add skeleton H/W debugger module support

This patch adds the skeleton H/W debugger module support. This code
enables registration and unregistration of a single HSA process at a
time.

The module saves the process's pasid and use it to verify that only the
registered process is allowed to execute debugger operations through the
kernel driver.

v2: rename get_dbgmgr_mutex to kfd_get_dbgmgr_mutex to namespace it

Signed-off-by: Yair Shachar <yair.shachar@amd.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>