soc: imx: gpcv2: Print the correct error code

The current code prints 'ret' (thus 0) while it should use 'err'.

Signed-off-by: Guido Günther <agx@sigxcpu.org>
Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>