gpu: ipu-v3: ipu-dmfc: Rename ipu_dmfc_init_channel to ipu_dmfc_config_wait4eot

The function name 'ipu_dmfc_config_wait4eot' matches the implementation of
the function better than 'ipu_dmfc_init_channel', since it only touches the
wait4eot bits.

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