accel/amdxdna: Declare sched_ops as static

Fix sparse warning:
  symbol 'sched_ops' was not declared. Should it be static?

Fixes: aac24309 ("accel/amdxdna: Add command execution")
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250113182617.1256094-2-lizhi.hou@amd.com