Revert "hwmon: (pmbus) Add regulator supply into macro"

This reverts commit 54cc3dbfc10dc3db7cb1cf49aee4477a8398fbde.

Zev Weiss reports that the reverted patch may cause a regulator
undercount. Here is his report:

... having regulator-dummy set as a supply on my PMBus regulators
(instead of having them as their own top-level regulators without
an upstream supply) leads to enable-count underflow errors when
disabling them:

# echo 0 > /sys/bus/platform/devices/efuse01/state
[ 906.094477] regulator-dummy: Underflow of regulator enable count
[ 906.100563] Failed to disable vout: -EINVAL
[ 136.992676] reg-userspace-consumer efuse01: Failed to configure state: -22

Zev reports that reverting the patch fixes the problem. So let's do that
for now.

Fixes: 54cc3dbfc10d ("hwmon: (pmbus) Add regulator supply into macro")
Cc: Marcello Sylvester Bauer <[e-mail]>
Reported-by: Zev Weiss <[e-mail]>
Signed-off-by: Guenter Roeck <[e-mail]>

drivers/hwmon/pmbus/pmbus.h

···
 #define PMBUS_REGULATOR_STEP(_name, _id, _voltages, _step)  \
 	[_id] = {						\
 		.name = (_name # _id),				\
-		.supply_name = "vin",				\
 		.id = (_id),					\
 		.of_match = of_match_ptr(_name # _id),		\
 		.regulators_node = of_match_ptr("regulators"),	\