boards/geprc-f722-v2: add F722 V2 declaration

boards/geprc-f722-v2/memory.x

@@ -0,0 +1,19 @@
+MEMORY
+{
+  FLASH : ORIGIN = 0x08000000, LENGTH = 512K
+  /*
+  * STM32F722 RAM totals 256 KiB:
+  *  - DTCM:  64 KiB at 0x2000_0000
+  *  - SRAM1: 176 KiB at 0x2001_0000
+  *  - SRAM2: 16 KiB at 0x2003_C000
+  *
+  * 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
+}