gpu: ipu-v3: Remove unused ipu_image_convert_* functions

gpu: ipu-v3: Remove unused ipu_image_convert_* functions

ipu_image_convert_enum_format() and ipu_image_convert_sync() were both
added in 2016 by
commit cd98e85a6b78 ("gpu: ipu-v3: Add queued image conversion support")

but have remained unused.

Remove them.

ipu_image_convert_sync() was the last user of
image_convert_sync_complete().

Remove it.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241226022752.219399-5-linux@treblig.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>