boards: silabs: siwx91x: Add support for DMAs

Report DMA configuration in the board definitions.

Note the addresses of the DMA buffers are hardcoded in the HAL. So,
these areas have to be declared in the linker file.

Co-authored-by: Sai Santhosh Malae <santhosh.malae@silabs.com>
Signed-off-by: Sai Santhosh Malae <santhosh.malae@silabs.com>
Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>

soc/silabs/silabs_siwx91x/siwg917/linker.ld

@@ -5,10 +5,29 @@
  */
 #include <zephyr/arch/arm/cortex_m/scripts/linker.ld>
 
+MEMORY
+{
+	udma0   (rwx)  : ORIGIN = 0x0002fc00, LENGTH = 0x00000400
+	udma1   (rwx)  : ORIGIN = 0x24061c00, LENGTH = 0x00000400
+}
+
 SECTIONS
 {
 	.common_tcm_code :
 	{
 		*(.common_tcm_code*)
 	} > FLASH
+
+	/* These regions of SRAM is where the UDMA descriptors are stored. The corresponding
+	   section must be properly declared in the linker script to ensure correct data transfer
+	   and proper functioning of the UDMA module */
+	.udma_addr0 :
+	{
+		*(.udma_addr0*)
+	} > udma0 AT> FLASH
+
+	.udma_addr1 :
+	{
+		*(.udma_addr1*)
+	} > udma1 AT> FLASH
 }