libpayload: Fix clang fallthrough warning

Clang does not recognize comments to indicate falltrough is intended
behavior.

Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Change-Id: Idcf7a24fc763b80863902702172b4ea950e132b8
Reviewed-on: https://review.coreboot.org/c/coreboot/+/77431
Reviewed-by: Martin L Roth <gaumless@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>

payloads/libpayload/curses/PDCurses/pdcurses/addch.c

@@ -173,8 +173,10 @@ int waddch(WINDOW *win, const chtype ch)
             /* don't back over left margin */
 
             if (--x < 0)
-        case '\r':
                 x = 0;
+            break;
+        case '\r':
+            x = 0;
 
             break;
 

payloads/libpayload/curses/PDCurses/pdcurses/scanw.c

@@ -274,7 +274,7 @@ static int _pdc_vsscanf(const char *buf, const char *fmt, va_list arg_ptr)
                             NEXT(c);
                             goto string;
                         }
-                        /* fall through */
+                        __fallthrough;
                     default:
                         if (fmt[1] == '-' && fmt[2]
                             && f < (unsigned char)fmt[2])