imx-drm: ipu-dmfc: Remove unneeded 'dmfc' check

Fix the following static checker warning:

drivers/staging/imx-drm/ipu-v3/ipu-dmfc.c:164 ipu_dmfc_setup_channel() warn: variable dereferenced before check 'dmfc' (see line 157)

As 'dmfc' could never be null, there is no need to do such check.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>