sim: Add a K64fMulti flash device

This device is similar to the K64f device, but it is twice as large, and
has the extra partitions needed to test multi-image.

Signed-off-by: David Brown <david.brown@linaro.org>
diff --git a/sim/src/lib.rs b/sim/src/lib.rs
index 43a1e5a..1778713 100644
--- a/sim/src/lib.rs
+++ b/sim/src/lib.rs
@@ -45,12 +45,13 @@
 }
 
 #[derive(Copy, Clone, Debug, Deserialize)]
-pub enum DeviceName { Stm32f4, K64f, K64fBig, Nrf52840, Nrf52840SpiFlash, }
+pub enum DeviceName { Stm32f4, K64f, K64fBig, K64fMulti, Nrf52840, Nrf52840SpiFlash, }
 
 pub static ALL_DEVICES: &'static [DeviceName] = &[
     DeviceName::Stm32f4,
     DeviceName::K64f,
     DeviceName::K64fBig,
+    DeviceName::K64fMulti,
     DeviceName::Nrf52840,
     DeviceName::Nrf52840SpiFlash,
 ];
@@ -61,6 +62,7 @@
             DeviceName::Stm32f4 => "stm32f4",
             DeviceName::K64f => "k64f",
             DeviceName::K64fBig => "k64fbig",
+            DeviceName::K64fMulti => "k64fmulti",
             DeviceName::Nrf52840 => "nrf52840",
             DeviceName::Nrf52840SpiFlash => "Nrf52840SpiFlash",
         };