media: i2c: imx219: Fix a bug in imx219_enum_frame_size

https://patchwork.linuxtv.org/patch/62740/

When enumerating the frame sizes, the value sent to
imx219_get_format_code should be fse->code
(the code from the ioctl) and not imx219->fmt.code
which is the code set currently in the driver.

Fixes: 22da1d56

 ("media: i2c: imx219: Add support for RAW8 bit bayer format")

Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Reviewed-by: Helen Koike <helen.koike@collabora.com>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>