power: supply: bq27xxx: Move one time design full read out of poll

power: supply: bq27xxx: Move one time design full read out of poll

This value only needs read once. Move that read into the function
that returns the value to keep the logic all in one place. This
also avoids doing this check every time we read in values in
the device update poll worker.

While here, correct this function's error message.

Signed-off-by: Andrew Davis <afd@ti.com>
Link: https://lore.kernel.org/r/20240123150914.308510-5-afd@ti.com
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>