convert all at91 files to use at91_gpio driver syntax

* convert all files cpu/../at91 to use at91_gpio driver syntax
 * change AT91_PINP([A-F])(\d+) to AT91_PIO_PORT\1, \2
   this makes all 160 AT91_PINPxxx defines obsolete
 * AT91_PINPxxx defines and gpio.h can be remove, if all boards converted to new SoC access

Signed-off-by: Jens Scharsig <js_at_ng@scharsoft.de>