Add dedicated section for pdm buffer

Author: pennam

targets/TARGET_STM/TARGET_STM32H7/TARGET_STM32H747xI/TARGET_PORTENTA_H7_M7/TOOLCHAIN_GCC_ARM/STM32H747xI.ld

@@ -32,8 +32,9 @@ MEMORY
   DTCMRAM (xrw)                 : ORIGIN = 0x20000000, LENGTH = 128K
   RAM (xrw)                     : ORIGIN = RAM_START + 0x298, LENGTH = RAM_SIZE - 0x298
   RAM_D2 (xrw)                  : ORIGIN = 0x30000000, LENGTH = 288K
-  OPENAMP_RSC_TAB (rwx)         : ORIGIN = 0x38000000, LENGTH = 1K
-  OPEN_AMP_SHMEM (rwx)          : ORIGIN = 0x38000400, LENGTH = 63K
+  RAM_D3 (xrw)                  : ORIGIN = 0x38000000, LENGTH = 1k
+  OPENAMP_RSC_TAB (rwx)         : ORIGIN = 0x38000400, LENGTH = 1K
+  OPEN_AMP_SHMEM (rwx)          : ORIGIN = 0x38000800, LENGTH = 62K
   FLASH (rx)                    : ORIGIN = MBED_APP_START, LENGTH = MBED_APP_SIZE
 }
  __OPENAMP_region_start__  = ORIGIN(OPEN_AMP_SHMEM);
@@ -187,8 +188,13 @@ SECTIONS
         __HeapLimit = .;
     } > RAM
 
-    .openamp_section (NOLOAD) : {
+    .ram_d3 (NOLOAD) : {
         . = ABSOLUTE(0x38000000);
+        *(.pdm_buffer)
+    } > RAM_D3
+
+    .openamp_section (NOLOAD) : {
+        . = ABSOLUTE(0x38000400);
         *(.resource_table)
     } >OPENAMP_RSC_TAB  AT > FLASH