free_up_channels can only be called once for a started transaction.
Double free will undesirely stop the next picked 2D-DMA transaction on the same channel.
- Add intr_priority field to gdma_channel_t structure
- Add intr_bind_name field to gdma_signal_conn_t for interrupt binding
- Validate intr_priority during channel allocation (must be 0-3)
- Use ESP_INTR_FLAG_SHARED_PRIVATE instead of ESP_INTR_FLAG_SHARED
- Use esp_intr_alloc_info() with bind_by.name for shared interrupts
- Add interrupt priority configuration test case
- Update all gdma_periph.c files with pair-specific bind names (gdma_gXpY)
