gpu: ipu-cpmem: remove unused ipu_cpmem_set_yuv_planar function

ipu_cpmem_set_yuv_planar_full is only used directly, remove the wrapper.

Suggested-by: Liu Ying <gnuiyl@gmail.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Liu Ying <gnuiyl@gmail.com>