drm/amdkfd: make SPDX License expression more sound

Commit b5f57384 ("drm/amdkfd: Add sysfs bitfields and enums to uAPI")
adds include/uapi/linux/kfd_sysfs.h with the "GPL-2.0 OR MIT WITH
Linux-syscall-note" SPDX-License expression.

The command ./scripts/spdxcheck.py warns:

  include/uapi/linux/kfd_sysfs.h: 1:48 Exception not valid for license MIT: Linux-syscall-note

For a uapi header, the file under GPLv2 License must be combined with the
Linux-syscall-note, but combining the MIT License with the
Linux-syscall-note makes no sense, as the note provides an exception for
GPL-licensed code, not for permissively licensed code.

So, reorganize the SPDX expression to only combine the note with the GPL
License condition. This makes spdxcheck happy again.

Fixes: b5f57384 ("drm/amdkfd: Add sysfs bitfields and enums to uAPI")
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by:  <kstewart@linuxfoundation.org>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>