Update hello world switch ports and default state

- Align the port definitions with actual switches on Nexus, and initialize the GPIO state by reading instead of always-zero (otherwise, on real hardware we always get a spurious change - since the switches are high when not pressed).

Change-Id: I7d3323a2d4cb60fbb03906c596ff0c817f2366ae

sw/device/examples/hello_world/hello_world.c

diff --git a/sw/device/examples/hello_world/hello_world.c b/sw/device/examples/hello_world/hello_world.c
index e24c7a8..216178b 100644
--- a/sw/device/examples/hello_world/hello_world.c
+++ b/sw/device/examples/hello_world/hello_world.c
@@ -32,10 +32,10 @@
 };
 
 static dif_pinmux_index_t switches[] = {
-    kTopMatchaPinmuxInselIoc8,
-    kTopMatchaPinmuxInselIoc5,
-    kTopMatchaPinmuxInselIoa2,
-    kTopMatchaPinmuxInselIoa3,
+    kTopMatchaPinmuxInselIor5,
+    kTopMatchaPinmuxInselIor6,
+    kTopMatchaPinmuxInselIor7,
+    kTopMatchaPinmuxInselIor10,
 };
 
 void configure_pinmux(void) {
@@ -116,7 +116,8 @@
   CHECK_DIF_OK(dif_spi_device_send(&spi, "SPI!", 4,
                                    /*bytes_sent=*/NULL));
 
-  uint32_t gpio_state = 0;
+  uint32_t gpio_state;
+  CHECK_DIF_OK(dif_gpio_read_all(&gpio, &gpio_state));
   while (true) {
     busy_spin_micros(10 * 1000);  // 10 ms
     gpio_state = demo_gpio_to_log_echo(&gpio, gpio_state);