media: i2c: st-mipid02: add Y8 format support

Add support of MEDIA_BUS_FMT_Y8_1X8.

Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>