tps65023: Allow registering similar TPS65021

TPS65021 is an older model and is slightly weaker (can supply less current),
otherwise is the same.

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>