spi_flash: add config option to override flash size in bootloader header

Sometimes the flash size read from bootloader is not correct. This may
forbid SPI Flash driver from reading the the area larger than the size
in bootloader header.

When the new config option is enabled, the latest configured
ESPTOOLPY_FLAHSIZE in the app header will be used to override the value
read from bootloader header.

components/bootloader_support/include/bootloader_flash_config.h

@@ -28,6 +28,14 @@ extern "C" {
  */
 void bootloader_flash_update_id(void);
 
+/**
+ * @brief Update the flash size in g_rom_flashchip (global esp_rom_spiflash_chip_t structure).
+ *
+ * @param size The size to store, in bytes.
+ * @return None
+ */
+void bootloader_flash_update_size(uint32_t size);
+
 /**
  * @brief Set the flash CS setup and hold time.
  *