[media] si2165: create function si2165_write_reg_list for writing register lists

It is common the need of writing a table of values. Add a function to provide a
helper to address such case. This will allow further code cleanups.

Signed-off-by: Matthias Schwarzott <zzam@gentoo.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>