fix: Fix the ESP32-S2 security info response size (#73)

The ESP32-S2 ROM GET_SECURITY_INFO
response does not contain chip_id and api_version fields.
Currently, the flasher stub just returns 0 and 0 for these, however
chip_id 0 is reserved for the ESP32.
This makes the stub behavior in line with the ROM.

Closes #65

src/targets.rs

@@ -50,7 +50,10 @@ extern "C" {
     fn spi_read_status_high(status: *const u32) -> u32;
 }
 
+#[cfg(not(feature = "esp32s2"))]
 const SECURITY_INFO_BYTES: usize = 20;
+#[cfg(feature = "esp32s2")]
+const SECURITY_INFO_BYTES: usize = 12;
 
 pub const FLASH_SECTOR_SIZE: u32 = 4096;
 pub const FLASH_BLOCK_SIZE: u32 = 65536;