drm/imx: fix typo in ipu_plane_formats[]

The BGRA8888 appears twice in the ipu_plane_formats[] list. The
duplicate should be BGRX8888.

The original commit is:

commit 59d6b718

 ("drm/imx: ipuv3-plane: enable support for RGBX8888
and RGBA8888 pixel formats")

Signed-off-by: Laurentiu Palcu <laurentiu.palcu@nxp.com>
Fixes: 59d6b718

 ("drm/imx: ipuv3-plane: enable support for RGBX8888 and RGBA8888 pixel")
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>