regulator: rtmv20: Fix .set_current_limit/.get_current_limit callbacks

Current code does not set .curr_table and .n_linear_ranges settings,
so it cannot use the regulator_get/set_current_limit_regmap helpers.
If we setup the curr_table, it will has 200 entries.
Implement customized .set_current_limit/.get_current_limit callbacks
instead.

Fixes: b8c054a5 ("regulator: rtmv20: Adds support for Richtek RTMV20 load switch regulator")
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Reviewed-by: ChiYuan Huang <cy_huang@richtek.com>
Link: https://lore.kernel.org/r/20210530124101.477727-1-axel.lin@ingics.com


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