Use regulator_set_ramp_delay_regmap instead of open-coded

LTC3589_LINEAR_REG() no longer call LTC3589_REG() now.
Only LTC3589_LINEAR_REG() needs to set go_bit, thus remove go_bit
parameter from LTC3589_REG() macro.
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Link: https://lore.kernel.org/r/20210604115803.1260976-1-axel.lin@ingics.comSigned-off-by: Mark Brown <broonie@kernel.org>