regulator: Check ramp_delay_table for regulator_set_ramp_delay_regmap

Return -EINVAL if ramp_delay_table is NULL.
Also add WARN_ON since the driver code needs fix if this happened.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Link: https://lore.kernel.org/r/20210519132255.1683863-1-axel.lin@ingics.com


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