drm/amd/sched: rename amd_sched_entity_pop_job

The function does not actually remove the job from the FIFO, so "peek"
describes it better.

Signed-off-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Andres Rodriguez <andresx7@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>