IO initial states are correct

lib/serial.c

@@ -0,0 +1,34 @@
+#include <serial.h>
+
+static serial_context ctx;
+
+serial_context *serial_get_context() {
+    return &ctx;
+};
+
+void serial_init() {
+    ctx.serial_control = 0x7E;
+    ctx.serial_data = 0;
+}
+
+void serial_write(u16 address, u8 value) {
+    if(address == 0xFF01) {
+        ctx.serial_data = value;
+        return;
+    }
+
+    if(address == 0xFF02) {
+        ctx.serial_control = value;
+        return;
+    }
+}
+
+u8 serial_read(u16 address) {
+    if(address == 0xFF01) {
+        return ctx.serial_data;
+    }
+
+    if(address == 0xFF02) {
+        return ctx.serial_control;
+    }
+}