refactor: move pl011/pl031 to be separate features

kernel/Cargo.toml

@@ -20,6 +20,9 @@ bitflags = "^1.3.0"
 cortex-a = { version = "6.x.x" }
 
 [features]
-mach_qemu = []
+pl011 = []
+pl031 = []
+
+mach_qemu = ["pl011", "pl031"]
 mach_orangepi3 = []
 mach_rpi3 = []

kernel/src/dev/rtc/mod.rs

@@ -2,6 +2,7 @@
 
 use crate::dev::Device;
 
+#[cfg(feature = "pl031")]
 pub mod pl031;
 
 // TODO define what RTC devices can do

kernel/src/dev/serial/mod.rs

@@ -3,6 +3,7 @@
 use crate::dev::Device;
 use error::Errno;
 
+#[cfg(feature = "pl011")]
 pub mod pl011;
 
 /// Generic interface for serial devices