small fix for defmt dependency

Author: robamu

cortex-ar/Cargo.toml

@@ -43,7 +43,7 @@ critical-section-single-core = ["critical-section"]
 # a CAS spinlock.
 critical-section-multi-core = ["critical-section"]
 # Adds defmt::Format implementation for the register types
-defmt = ["dep:defmt"]
+defmt = ["dep:defmt", "arbitrary-int/defmt"]
 
 [package.metadata.docs.rs]
 targets = ["armv7r-none-eabihf", "armv7r-none-eabi", "armv7a-none-eabihf"]