radeonsi: set a per-buffer flag that disables inter-process sharing (v4)

radeonsi: set a per-buffer flag that disables inter-process sharing (v4)

For lower overhead in the CS ioctl.
Winsys allocators are not used with interprocess-sharable resources.

v2: It shouldn't crash anymore, but the kernel will reject the new flag.
v3 (christian): Rename the flag, avoid sending those buffers in the BO list.
v4 (christian): Remove setting the kernel flag for now

Reviewed-by: Marek Olšák <marek.olsak@amd.com>