scd: Fix parameter name of app_change_key.

* scd/app-common.h (APP_GENKEY_FLAG_FORCE): New.
* scd/app.c (app_change_pin): Rename arg reset_mode to flags and
change from int to unsigned int.

This is basically a documentation fix.

(cherry picked from commit c26af8ac263ea006ed32e110a09271e4bfbf1f37)

• Signed-off-by: Werner Koch <wk@gnupg.org>