media: platform: exynos4-is: Remove unused fimc_is_param_strerr

fimc_is_param_strerr() was added in 2013 by
commit 9a761e43 ("[media] exynos4-is: Add Exynos4x12 FIMC-IS driver")
but has never been called.

Remove it.

(The other possibility might be to add a call maybe in fimc-is-param ?)

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>