video: fbdev: imxfb: Fix an error message

'ret' is known to be 0 here.
No error code is available, so just remove it from the error message.

Fixes: 72330b0e ("i.MX Framebuffer: Use readl/writel instead of direct pointer deref")
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/d7b25026f82659da3c6f7159eea480faa9d738be.1620327302.git.christophe.jaillet@wanadoo.fr