power: supply: bd70528: rename linear_range to avoid collision

Follow-up patches in this series will add a generic struct
linear_range. Rename bd70528 internal struct to avoid collision.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/286b1ae0adc1c08e7b644cbdc1a43eb2e0644647.1588944082.git.matti.vaittinen@fi.rohmeurope.com


Signed-off-by: Mark Brown <broonie@kernel.org>