regulator: doc: remove documentation comment for regulator_init

Remove documentation comment related to regulator_init callback.
This solves the following warning when building the kernel documentation:

./include/linux/regulator/machine.h:290: warning: Excess struct member 'regulator_init' description in 'regulator_init_data'

Fixes: 602ff58ae4fe ("regulator: core: remove machine init callback from config")
Reported-by: Stephen Rothwell <[e-mail]>
Closes: https://lore.kernel.org/lkml/[e-mail]/
Signed-off-by: Jerome Brunet <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

include/linux/regulator/machine.h

···
  *               be usable.
  * @num_consumer_supplies: Number of consumer device supplies.
  * @consumer_supplies: Consumer device supply configuration.
- *
- * @regulator_init: Callback invoked when the regulator has been registered.
  * @driver_data: Data passed to regulator_init.
  */
 struct regulator_init_data {