Correct address for STM32F2 flash size register

There was a typo in the flash size register address for STM32F2. Change
to correct address. Verified against STM32F207 reference manual
(RM0033 Rev 5 section 33.2), and an STM32F217 chip.

src/stlink-common.h

@@ -161,7 +161,7 @@ static const chip_params_t devices[] = {
         {  // table 1, PM0059
             .chip_id = STM32_CHIPID_F2,
                     .description = "F2 device",
-                    .flash_size_reg = 0x1ff7a22, /* RM0033 sind Rev 4*/
+                    .flash_size_reg = 0x1fff7a22, /* As in RM0033 Rev 5*/
                     .flash_pagesize = 0x20000,
                     .sram_size = 0x20000,
                     .bootrom_base = 0x1fff0000,