regulator: core: fix use_count leakage when handling boot-on

In the Linux kernel, the following vulnerability has been resolved:

regulator: core: fix use_count leakage when handling boot-on

I found a use_count leakage towards supply regulator of rdev with

boot-on option.

┌───────────────────┐ ┌───────────────────┐

│ regulator_dev A │ │ regulator_dev B │

│ (boot-on) │ │ (boot-on) │

│ use_count=0 │◀──supply──│ use_count=1 │

│ │ │ │

└───────────────────┘ └───────────────────┘

In case of rdev(A) configured with `regulator-boot-on', the use_count

of supplying regulator(B) will increment inside

regulator_enable(rdev->supply).

Thus, B will acts like always-on, and further balanced

regulator_enable/disable cannot actually disable it anymore.

However, B was also configured with `regulator-boot-on', we wish it

could be disabled afterwards.