Allow compile-time override of detected flash size.

On the STM32F103C8, as used in the "blue pill" boards, it has been
determined that, despite these only officially having 64KiB flash, it is
possible to actually use 128KiB of flash.

This commit allows for a preprocessor define
STM32F103_OVERRIDE_FLASH_SIZE which, when set, is used as the size of
flash in KiB instead of reading it from the FLASH_SIZE_REG.

AUTHORS

@@ -2,6 +2,10 @@ Aidan Thornton:
     Added Maple Mini support.
 	board/board-maple-mini.h
 
+Jeremy Drake:
+    Modified STM32F103 support.
+	mcu/sys-stm32f103.c
+
 Kaz Kojima:
     Added STM32 Primer2 support.
 	board/board-stm32-primer2.h

ChangeLog

@@ -1,3 +1,8 @@
+2017-08-03  Jeremy Drake <jeremydrake+gnuk@eacceleration.com>
+
+	* mcu/sys-stm32f103.c (flash_write): Allow compile time
+	flash size definition by STM32F103_OVERRIDE_FLASH_SIZE_KB.
+
 2017-08-02  NIIBE Yutaka  <gniibe@fsij.org>
 
 	* contrib/adc-gnu-linux.c: New.

mcu/sys-stm32f103.c

@@ -213,7 +213,11 @@ static int
 flash_write (uint32_t dst_addr, const uint8_t *src, size_t len)
 {
   int status;
+#if defined(STM32F103_OVERRIDE_FLASH_SIZE_KB)
+  uint32_t flash_end = FLASH_START_ADDR + STM32F103_OVERRIDE_FLASH_SIZE_KB*1024;
+#else
   uint32_t flash_end = FLASH_START_ADDR + (*FLASH_SIZE_REG)*1024;
+#endif
 
   if (dst_addr < FLASH_START || dst_addr + len > flash_end)
     return 0;
@@ -269,7 +273,11 @@ static void __attribute__((naked))
 flash_erase_all_and_exec (void (*entry)(void))
 {
   uint32_t addr = FLASH_START;
+#if defined(STM32F103_OVERRIDE_FLASH_SIZE_KB)
+  uint32_t end = FLASH_START_ADDR + STM32F103_OVERRIDE_FLASH_SIZE_KB*1024;
+#else
   uint32_t end = FLASH_START_ADDR + (*FLASH_SIZE_REG)*1024;
+#endif
   uint32_t page_size = 1024;
   int r;