pinctrl: at91 add deglitch, debounce, pull down and schmitt trigger mux option support

add :
 set_deglitch: enable/disable deglitch
 set_debounce: enable/disable debounce
 set_pulldown: enable/disable pulldown
 disable_schmitt_trig: disable schmitt trigger

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>