regulator: consumer.rst: document bulk operations

regulator: consumer.rst: document bulk operations

The current consumer documentation does not include bulk operations,
providing an example of how to acquire multiple regulators by calling
regulator_get() multiple times. That solution is valid and slightly
simpler for a small amount of regulators, but it does not scale well.

Document the bulk operations to get, enable and disable regulators.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://patch.msgid.link/20250819-reg_consumer_doc-v1-1-b631fc0d35a3@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>