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, 9 insertions, 0 deletions

diff --git a/src/lib.rs b/src/lib.rs
index fb204d27b..d3560e651 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -6,6 +6,7 @@
 // #![doc = document_features::document_features!(feature_label = r#"<span class="stab portability"><code>{feature}</code></span>"#)]
 
 pub mod clocks; // still provide clock helpers
+pub mod dma;
 pub mod gpio;
 pub mod pins; // pin mux helpers
 
@@ -51,6 +52,14 @@ embassy_hal_internal::peripherals!(
 
     DBGMAILBOX,
     DMA0,
+    DMA_CH0,
+    DMA_CH1,
+    DMA_CH2,
+    DMA_CH3,
+    DMA_CH4,
+    DMA_CH5,
+    DMA_CH6,
+    DMA_CH7,
     EDMA0_TCD0,
     EIM0,
     EQDC0,