media: i2c: st-vgxy61: Fix control flow error on probe

In case of error 'update_hdr' now goes through 'power_off' instead of
returning, effectively shutting down the sensor.

Signed-off-by: Benjamin Mugnier <benjamin.mugnier@foss.st.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>