drm/uapi: add explicit virtgpu context debug name

There are two problems with the current method of determining the
virtio-gpu debug name.

1) TASK_COMM_LEN is defined to be 16 bytes only, and this is a
   Linux kernel idiom (see PR_SET_NAME + PR_GET_NAME). Though,
   Android/FreeBSD get around this via setprogname(..)/getprogname(..)
   in libc.

   On Android, names longer than 16 bytes are common.  For example,
   one often encounters a program like "com.android.systemui".

   The virtio-gpu spec allows the debug name to be up to 64 bytes, so
   ideally userspace should be able to set debug names up to 64 bytes.

2) The current implementation determines the debug name using whatever
   task initiated virtgpu.  This is could be a "RenderThread" of a
   larger program, when we actually want to propagate the debug name
   of the program.

To fix these issues, add a new CONTEXT_INIT param that allows userspace
to set the debug name when creating a context.

It takes a null-terminated C-string as the param value. The length of the
string (excluding the terminator) **should** be <= 64 bytes.  Otherwise,
the debug_name will be truncated to 64 bytes.

Link to open-source userspace:
https://android-review.googlesource.com/c/platform/hardware/google/gfxstream/+/2787176



Signed-off-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: Josh Simonot <josh.simonot@gmail.com>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231018181727.772-2-gurchetansingh@chromium.org