Bluetooth: Mesh: Fix re-initializing provisioning state upon reset

If both PB-ADV and PB-GATT are supported, we need to properly
re-initialize variables such as link.rx.prev_id and (particularly
importantly) link.rx.buf. If we don't do this it may lead to the
following fault when trying to reprovision again:

***** USAGE FAULT *****
  Illegal use of the EPSR
***** Hardware exception *****
Current thread ID = 0x20001f10
Faulting instruction address = 0x0
Fatal fault in thread 0x20001f10! Aborting.

Fixes #14928

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
1 file changed