media: rcar-csi2: Allow writing any code and data value to PHTW

The helper to write an array of code and data values to the PHY Test
Interface Write Register (PHTW) register uses the case where both code
and data are zero as an exit condition. This prevents writing data = 0
and code = 0 to the register.

Up until now this has been OK as no such combination where needed, and
it was a convenient exit condition. In future writing data = 0 and code
= 0 to the PHTW register will be needed.

Avoid using an exit condition when writing an array of PHTW values and
instead pass the length of the array to the helper. This allows any
combination of code and data to be written.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>