Update hello world to check the correct switch pins

- Looks like the mask was changed at some point, but not the actual pin indices.

Change-Id: Ibf6834a30ebf1a8803ecd6eef95f6b1bf804af04

sw/device/examples/demos.c

diff --git a/sw/device/examples/demos.c b/sw/device/examples/demos.c
index bb8fde1..c9f69a8 100644
--- a/sw/device/examples/demos.c
+++ b/sw/device/examples/demos.c
@@ -43,7 +43,7 @@
   gpio_state &= kGpioMask;
 
   uint32_t state_delta = prev_gpio_state ^ gpio_state;
-  for (int bit_idx = 0; bit_idx < 8; ++bit_idx) {
+  for (int bit_idx = 8; bit_idx <= 11; ++bit_idx) {
     bool changed = ((state_delta >> bit_idx) & 0x1) != 0;
     bool is_currently_set = ((gpio_state >> bit_idx) & 0x1) != 0;
     if (changed) {