Bind RMT channel interrupts by module name and allocate them as private
shared so channels in the same RMT instance reuse one CPU interrupt line
without exposing it to other peripherals. Drop RMT-side interrupt
priority conflict state and let the interrupt allocator enforce
compatibility.
Use soc_rmt_signals[group_id].module_name when creating RMT PM locks and
drop the per-channel formatted lock name buffer. This keeps naming
consistent with interrupt binding and removes unnecessary string
formatting state.
