stm32/boards/STM32F769DISC: Fix length of FLASH_APP section.

Fixes issue #4924.

ports/stm32/boards/STM32F769DISC/f769_qspi.ld

@@ -17,7 +17,7 @@
 
 MEMORY
 {
-    FLASH_APP (rx)  : ORIGIN = 0x08020000, LENGTH = 2016K   /* sectors 1-11 3x32K 1*128K 7*256K */
+    FLASH_APP (rx)  : ORIGIN = 0x08020000, LENGTH = 1920K   /* sectors 4-11 1*128K 7*256K */
     FLASH_QSPI (rx) : ORIGIN = 0x90000000, LENGTH = 64M     /* external QSPI flash in XIP mode */
     DTCM (xrw)      : ORIGIN = 0x20000000, LENGTH = 128K    /* Used for storage cache */
     RAM (xrw)       : ORIGIN = 0x20020000, LENGTH = 384K    /* SRAM1 = 368K, SRAM2 = 16K */