drm/scheduler: Fix variable name in function description

Compiling AMD GPU drivers displays two warnings:

drivers/gpu/drm/scheduler/sched_main.c:738: warning: Function parameter or member 'file' not described in 'drm_sched_job_add_syncobj_dependency'
drivers/gpu/drm/scheduler/sched_main.c:738: warning: Excess function
parameter 'file_private' description in
'drm_sched_job_add_syncobj_dependency'

Get rid of them by renaming the variable name on the function description

Signed-off-by: Caio Novais <caionovais@usp.br>
Link: https://lore.kernel.org/r/20230325131532.6356-1-caionovais@usp.br
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>