platform/nrf_pca10001: Only expose currently used GPIO pins
platform/nrf_pca10001: Only expose currently used GPIO pins

LED_0 in particular is used in c_blinky app. To avoiding #ifdef'ing
userspace, assign it same index as LED_0 on storm platform.

The ideal solution is to have a LED driver that abstracts this.

google/tock-on-titan,google/tock-on-titan,google/tock-on-titan