regulator: core: fix locking in regulator_resolve_supply() error path

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

regulator: core: fix locking in regulator_resolve_supply() error path

If late enabling of a supply regulator fails in

regulator_resolve_supply(), the code currently triggers a lockdep

warning:

WARNING: drivers/regulator/core.c:2649 at _regulator_put+0x80/0xa0, CPU#6: kworker/u32:4/596

...

Call trace:

_regulator_put+0x80/0xa0 (P)

regulator_resolve_supply+0x7cc/0xbe0

regulator_register_resolve_supply+0x28/0xb8

as the regulator_list_mutex must be held when calling _regulator_put().

To solve this, simply switch to using regulator_put().

While at it, we should also make sure that no concurrent access happens

to our rdev while we clear out the supply pointer. Add appropriate

locking to ensure that.

While the code in question will be removed altogether in a follow-up

commit, I believe it is still beneficial to have this corrected before

removal for future reference.