Replace \n to \r\n in serial driver

Signed-off-by: Harry Chen <i@harrychen.xyz>

kernel/src/drivers/serial/16550_reg.rs

@@ -68,14 +68,21 @@ impl SerialPort {
 impl Write for SerialPort {
     fn write_str(&mut self, s: &str) -> Result {
         for c in s.bytes() {
-            if c == 127 {
+            match c {
+                127 => {
                     self.putchar(8);
                     self.putchar(b' ');
                     self.putchar(8);
-            } else {
+                },
+                b'\n' => {
+                    self.putchar(b'\r');
+                    self.putchar(b'\n');
+                },
+                c => {
                     self.putchar(c);
                 }
             }
+        }
         Ok(())
     }
 }

kernel/src/drivers/serial/simple_uart.rs

@@ -59,14 +59,21 @@ impl SerialPort {
 impl Write for SerialPort {
     fn write_str(&mut self, s: &str) -> Result {
         for c in s.bytes() {
-            if c == 127 {
+            match c {
+                127 => {
                     self.putchar(8);
                     self.putchar(b' ');
                     self.putchar(8);
-            } else {
+                },
+                b'\n' => {
+                    self.putchar(b'\r');
+                    self.putchar(b'\n');
+                },
+                c => {
                     self.putchar(c);
                 }
             }
+        }
         Ok(())
     }
 }

kernel/src/drivers/serial/ti_16c550c.rs

@@ -68,14 +68,21 @@ impl SerialPort {
 impl Write for SerialPort {
     fn write_str(&mut self, s: &str) -> Result {
         for c in s.bytes() {
-            if c == 127 {
+            match c {
+                127 => {
                     self.putchar(8);
                     self.putchar(b' ');
                     self.putchar(8);
-            } else {
+                },
+                b'\n' => {
+                    self.putchar(b'\r');
+                    self.putchar(b'\n');
+                },
+                c => {
                     self.putchar(c);
                 }
             }
+        }
         Ok(())
     }
 }