Generalize load_engine_and_select_page by reworking the implementation
and making it part of the generic load_engine function.

Add a new option in device_config, pages_per_engine used to define pages
assigned to each engine. With this option set, it's assumed LED chip
supports pages and load_engine will correctly setup the write page.

An equal amount of pages is assigned to each engine and they are
assigned from page 0.

Update any lp55xx based LED driver to define the option and use the new
function.
Suggested-by: Lee Jones <lee@kernel.org>
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Link: https://lore.kernel.org/r/20240626160027.19703-7-ansuelsmth@gmail.comSigned-off-by: Lee Jones <lee@kernel.org>