V4L/DVB (5815): Cx88: i2c structure templates clean-up

Clean up the use of structure templates in cx88-i2c and cx88-vp3054-i2c.
For one thing, a real template is supposed to be read-only. And in some
cases it's more efficient to initialize the few fields we need
individually.

This clean-up shrinks cx88-i2c.o by 33% and cx88-vp3054-i2c.o by 49%
(x86_64).

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>