ref(fallthrough): Change the fallthrough annotation to attribute

Clang compiler only accepts fallthrough annotation to be done using
attribute(fallthrough). This is can be enforced in gcc using the flag
-Wimplicit-fallthrough=5

Signed-off-by: Miguel Silva <[email protected]>

Author: miguelafsilva5

src/lib/printk.c

@@ -123,10 +123,10 @@ size_t vsnprintk(char* buf, size_t buf_size, const char** fmt, va_list* args)
                     case 'x':
                     case 'X':
                         flags = flags | F_BASE16;
-                    /* fallthrough */
+                        __attribute__((fallthrough));
                     case 'u':
                         flags = flags | F_UNSIGNED;
-                    /* fallthrough */
+                        __attribute__((fallthrough));
                     case 'd':
                     case 'i':
                         va_copy(args_tmp, *args);