linux-imx

drm/imx: dpu: kms: Ensure array idx k >= 0 before accessing sources[]

This patch checks array index 'k' in function
dpu_atomic_assign_plane_source_per_crtc() to make sure it's
no less than zero before using it to access array sources[].

Signed-off-by: Liu Ying <victor.liu@nxp.com>