drivers/usart: remove orphan Cargo.toml files

drivers/usart/api/Cargo.toml

diff --git a/drivers/usart/api/Cargo.toml b/drivers/usart/api/Cargo.toml
deleted file mode 100644
index e41bc52..0000000
--- a/drivers/usart/api/Cargo.toml
+++ /dev/null
@@ -1,8 +0,0 @@
-[package]
-name = "usart-api"
-version = "0.1.0"
-edition = "2024"
-
-[dependencies]
-bitflags = { version = "2", default-features = false }
-zerocopy = { version = "0.8", default-features = false, features = ["derive"] }

drivers/usart/client/Cargo.toml

diff --git a/drivers/usart/client/Cargo.toml b/drivers/usart/client/Cargo.toml
deleted file mode 100644
index f14e134..0000000
--- a/drivers/usart/client/Cargo.toml
+++ /dev/null
@@ -1,7 +0,0 @@
-[package]
-name = "usart-client"
-version = "0.1.0"
-edition = "2024"
-
-[dependencies]
-usart-api = { path = "../api" }

drivers/usart/server/Cargo.toml

diff --git a/drivers/usart/server/Cargo.toml b/drivers/usart/server/Cargo.toml
deleted file mode 100644
index 9c6cfd0..0000000
--- a/drivers/usart/server/Cargo.toml
+++ /dev/null
@@ -1,7 +0,0 @@
-[package]
-name = "usart-server"
-version = "0.1.0"
-edition = "2024"
-
-[dependencies]
-usart-api = { path = "../api" }