feat(dma): add DMA driver with 10 verified examples

Initial DMA driver implementation for MCXA276 with:

Core DMA Features:
- DmaChannel type with ownership tracking via Channel trait
- Transfer, RingBuffer, and ScatterGatherBuilder abstractions
- Support for mem-to-mem, mem-to-peripheral, peripheral-to-mem transfers
- Interrupt-driven completion with embassy async/await integration
- Word size abstraction (u8, u16, u32) via Word trait

LPUART DMA Integration:
- LpuartTxDma and LpuartRxDma drivers for async UART with DMA
- LpuartDma combined TX/RX driver
- Automatic chunking for buffers > 0x7FFF bytes
- DMA guards with Drop impl for safe cancellation

10 Verified Examples:
- dma_mem2mem: Basic memory-to-memory copy
- dma_memset: Memory fill with pattern
- dma_uart_tx: UART transmit via DMA
- dma_uart_rx: UART receive via DMA
- dma_uart_loopback: Combined TX/RX loopback test
- dma_scatter_gather: Linked descriptor chains
- dma_channel_linking: Major/minor loop channel linking
- dma_ring_buffer: Circular buffer for continuous streaming
- dma_ping_pong: Double-buffering pattern
- dma_software_trigger: Manual transfer triggering

PR Feedback Addressed:
- Use PAC accessor for LPUART DATA register instead of manual offset
- Add EnableInterrupt enum to replace boolean parameter for readability
- Add DMA guards with Drop impl for safe async cancellation
- Automatic chunking for large buffers instead of returning error
- Use NonNull<[W]> + PhantomData for RingBuffer (DMA acts like separate thread)
- Remove edma parameter from all methods (single eDMA instance steals ptr internally)
- Make edma_tcd() non-public (HAL should not expose PAC items)

1 files changed, 7 insertions, 0 deletions

diff --git a/src/clocks/mod.rs b/src/clocks/mod.rs
index 9c9e6ef3d..ac30115f6 100644
--- a/src/clocks/mod.rs
+++ b/src/clocks/mod.rs
@@ -399,6 +399,10 @@ pub unsafe fn assert_reset<G: Gate>() {
 }
 
 /// Check whether the peripheral is held in reset.
+///
+/// # Safety
+///
+/// Must be called with a valid peripheral gate type.
 #[inline]
 pub unsafe fn is_reset_released<G: Gate>() -> bool {
     G::is_reset_released()
@@ -940,4 +944,7 @@ pub(crate) mod gate {
     impl_cc_gate!(LPUART4, mrcc_glb_cc0, mrcc_glb_rst0, lpuart4, LpuartConfig);
     impl_cc_gate!(LPUART5, mrcc_glb_cc1, mrcc_glb_rst1, lpuart5, LpuartConfig);
     impl_cc_gate!(ADC1, mrcc_glb_cc1, mrcc_glb_rst1, adc1, AdcConfig);
+
+    // DMA0 peripheral - uses NoConfig since it has no selectable clock source
+    impl_cc_gate!(DMA0, mrcc_glb_cc0, mrcc_glb_rst0, dma0, NoConfig);
 }