drm/xe/ads: Use flexible-array

drm/xe/ads: Use flexible-array

Zero-length arrays are deprecated and flexible arrays should be
used instead: https://www.kernel.org/doc/html/v6.9-rc7/process/deprecated.html#zero-length-and-one-element-arrays

Reported-by: kernel test robot <[email protected]>
Reported-by: Julia Lawall <[email protected]>
Closes: https://lore.kernel.org/r/[email protected]/
Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Cc: Matthew Brost <[email protected]>
Reviewed-by: Matthew Brost <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Lucas De Marchi <[email protected]>
(cherry picked from commit ee7284230644e21fef0e38fc5bf8f907b6bb7f7c)
Signed-off-by: Lucas De Marchi <[email protected]>