protect BL flash section on linker script

Author: alejandrogonzalvo

STM32H723ZGTX_FLASH.ld

@@ -45,7 +45,7 @@ MEMORY
 {
   ITCMRAM (xrw)    : ORIGIN = 0x00000000,   LENGTH = 64K
   DTCMRAM (xrw)    : ORIGIN = 0x20000000,   LENGTH = 128K
-  FLASH    (rx)    : ORIGIN = 0x08000000,   LENGTH = 1024K
+  FLASH    (rx)    : ORIGIN = 0x08000000,   LENGTH = 1024K-128K
   RAM_D1  (xrw)    : ORIGIN = 0x24000000,   LENGTH = 320K
   RAM_D2  (xrw)    : ORIGIN = 0x30000000,   LENGTH = 32K
   RAM_D3  (xrw)    : ORIGIN = 0x38000000,   LENGTH = 16K