Attempt to fix min-versions

Cargo.toml

@@ -28,6 +28,7 @@ embedded-io = "0.6.1"
 # Fix for min-versions.
 # TODO: remove once unnecessary.
 ral-registers = ">= 0.1.3"
+eh-old = { package = "embedded-hal", version = "0.2.6" }
 
 [dev-dependencies]
 teensy4-bsp = { version = "0.5.0", features = ["rt"] }