media: i2c: vd55g1: Fix duster register address

The duster register needs to be disabled on test patterns. While the
code is correctly doing so, the register address contained a typo, thus
not disabling the duster correctly. Fix the typo.

Fixes: e56616d7 ("media: i2c: Add driver for ST VD55G1 camera sensor")

Signed-off-by: Benjamin Mugnier <benjamin.mugnier@foss.st.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>