gpio:Initial GPIO driver.(ARM)

Small GPIO driver that exports a few pins using a virtual file
system. Currently the two user leds and the user button are exported.

Change-Id: I001d017ae27cd17b635587873f7da981054da459
vm: fix kernel-requested mappings for arm

	. make vm tell kernel virtual locations of mappings
	. makes _minix_kerninfo feature work
	. fix for mappings being larger than what 1 pde can address
	  (e.g. devices memory requested on arm)
	. still requires a special case for devices memory for the
	  kernel, which has to switch to virtual addressing

Change-Id: I2e94090aa432346fa4da0edeba72f0b7406c2ad7