drivers/gpu/drm/amd/amdkfd: use in_compat_syscall to check open() caller type

amdkfd wants to know syscall type, not task type.  Check directly.

Unfortunately, amdkfd is making nasty assumptions that a process'
bitness is a well-defined constant thing.  This isn't the case on x86.
I don't know how much this matters, but this patch has no effect on
generated code on x86, so amdkfd is equally broken with and without this
patch.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Oded Gabbay <oded.gabbay@gmail.com>
Cc: David Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>