sim: Remove extraneous static

According to clippy, `&'static` can just be `&` for static definitions,
which always have a static lifetime.  Clean this up in the arrays in the
code, as well as generation code in imgtool.

Signed-off-by: David Brown <david.brown@linaro.org>
diff --git a/sim/src/lib.rs b/sim/src/lib.rs
index 93cdbfa..e602327 100644
--- a/sim/src/lib.rs
+++ b/sim/src/lib.rs
@@ -33,7 +33,7 @@
     },
 };
 
-const USAGE: &'static str = "
+const USAGE: &str = "
 Mcuboot simulator
 
 Usage:
@@ -67,7 +67,7 @@
     Nrf52840UnequalSlots,
 }
 
-pub static ALL_DEVICES: &'static [DeviceName] = &[
+pub static ALL_DEVICES: &[DeviceName] = &[
     DeviceName::Stm32f4,
     DeviceName::K64f,
     DeviceName::K64fBig,