pac55xx: gpio: Initial Implementation of PAC55xx GPIO Driver

* Conforms mostly to the STM32 GPIO API where possible.
* Supports pin configuration (direction, pull-up/down, etc.) as well
  as pinmux configuration.
* Supports set/clear/get operations to the GPIO port/pins.
* Created base doxy header and groups to align with existing formatting.

lib/pac55xx/vector_chipset.c

@@ -18,8 +18,7 @@
  */
 
 /* Standard Cortex-M4F initialization of FPU. */
-static void pre_main(void)
-{
+static void pre_main(void) {
 	/* Enable FPU */
 	SCB_CPACR |= SCB_CPACR_FULL * (SCB_CPACR_CP10 | SCB_CPACR_CP11);
 }