screen: fix backspace handling

src/drivers/screen.c

@@ -95,7 +95,15 @@ void terminal_putchar(char c)
 		return;
 	}
 
-	if (c == '\n') {
+	if (c == '\b') {
+        if (terminal_column > 0) {
+            terminal_column--;
+        } else if (terminal_row > 0) {
+            terminal_row--;
+            terminal_column = VGA_WIDTH - 1;
+        }
+    }
+	else if (c == '\n') {
 		terminal_column = 0;
 		terminal_row++;
 	} else {