drm/amdkfd: CRIU Introduce Checkpoint-Restore APIs

Checkpoint-Restore in userspace (CRIU) is a powerful tool that can
snapshot a running process and later restore it on same or a remote
machine but expects the processes that have a device file (e.g. GPU)
associated with them, provide necessary driver support to assist CRIU
and its extensible plugin interface. Thus, In order to support the
Checkpoint-Restore of any ROCm process, the AMD Radeon Open Compute
Kernel driver, needs to provide a set of new APIs that provide
necessary VRAM metadata and its contents to a userspace component
(CRIU plugin) that can store it in form of image files.

This introduces some new ioctls which will be used to checkpoint-Restore
any KFD bound user process. KFD only allows ioctl calls from the same
process that opened the KFD file descriptor. Since these ioctls are
expected to be called from a KFD criu plugin which has elevated ptrace
attached privileges and CAP_CHECKPOINT_RESTORE capabilities attached with
the file descriptors so modify KFD to allow such calls.

(API redesigned by David Yat Sin)
Suggested-by: Felix Kuehling <felix.kuehling@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: David Yat Sin <david.yatsin@amd.com>
Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>