migrate read and write volatile to a function

src/lib.rs

@@ -1,6 +1,17 @@
 #![no_std]
 
+use core::ptr::{read_volatile, write_volatile};
+
 pub mod peripherals;
 
 pub mod irq_interrupt;
+pub mod mailbox;
 pub mod timer;
+
+pub fn mmio_read(address: u32) -> u32 {
+    unsafe { read_volatile(address as *const u32) }
+}
+
+pub fn mmio_write(address: u32, data: u32) {
+    unsafe { write_volatile(address as *mut u32, data) }
+}