boards/kakute-f7-mini-v3: fix invalid memory layout

Signed-off-by: Onur Özkan <work@onurozkan.dev>

boards/kakute-f7-mini-v3/memory.x

@@ -1,20 +1,19 @@
 MEMORY
 {
   FLASH : ORIGIN = 0x08000000, LENGTH = 512K
-
   /*
-   * STM32F722 RAM totals 256 KiB:
-   * - DTCM:  64 KiB at 0x2000_0000; inaccessible to DMA1 and DMA2.
-   * - SRAM1: 176 KiB at 0x2001_0000; contiguous and DMA2-accessible.
-   * - SRAM2:  16 KiB at 0x2004_C000; a separate bank after an address gap.
-   *
-  * Why use SRAM1 as the only default RAM region: the MPU6000 SPI DMA buffers
-  * and USART1 TX DMA frames are ordinary RTIC task-local/static allocations.
-  * Mapping `RAM` to DTCM would let the linker place those buffers where DMA2
-  * cannot read or write them which would lead transfer faults or corrupted data.
+  * STM32F722 RAM totals 256 KiB:
+  *  - DTCM:  64 KiB at 0x2000_0000
+  *  - SRAM1: 176 KiB at 0x2001_0000
+  *  - SRAM2: 16 KiB at 0x2003_C000
   *
-  * Therefore all default allocations use SRAM1 to make DMA reachability the
-  * safe default rather than a per-buffer convention.
-   */
-  RAM : ORIGIN = 0x20010000, LENGTH = 176K
+  * SRAM1 and SRAM2 are contiguous and are both accessible by DMA1 and DMA2.
+  * They form one 192 KiB default RAM region from 0x2001_0000 through
+  * 0x2003_FFFF. DTCM is intentionally kept separate for a future explicit
+  * placement policy rather than mixing CPU-critical and general allocations.
+  *
+  * TODO: Utilize DTCM.
+  *
+  */
+  RAM : ORIGIN = 0x20010000, LENGTH = 192K
 }