add __NOPs to stop dodgy busy-wait loops being optimised out0

Really need to get on top of these

firmware/src/gps_osp.c

@@ -1143,7 +1143,7 @@ void gps_init(void)
   /* ---- GPS Configuration ---- */
 
   /* We need to wait for the GPS 32kHz clock to start (~300ms). TODO: more robust method for this */
-  for (int i = 0; i < 300*1000; i++);
+  for (int i = 0; i < 300*1000; i++) { __NOP(); }
 
   /* Close any currently running session. Doesn't do anything unless debugging */
   //osp_reset_initialise();       /* hopefully don't need this now */
@@ -1164,7 +1164,7 @@ void gps_reinit(void)
 
   /* Wait for about 3 seconds, kicking the watchdog along the way. TODO: more robust method for this */
   for (int j = 0; j < 10; j++) {
-    for (int i = 0; i < 300*1000; i++);
+    for (int i = 0; i < 300*1000; i++) { __NOP(); }
     kick_the_watchdog();
   }
 

firmware/src/si_trx.c

@@ -145,7 +145,7 @@ void _si_trx_transfer(int tx_count, int rx_count, uint8_t *data)
    */
 
   do {
-    for (int i = 0; i < 200; i++); /* Approx. 20µS */
+    for (int i = 0; i < 200; i++) { __NOP(); } /* Approx. 20µS */
     _si_trx_cs_enable();
 
     /* Issue READ_CMD_BUFF */
@@ -547,7 +547,7 @@ void si_trx_reset(uint8_t modulation_type, struct si_frequency_configuration* fc
   /* We expect to already be shutdown  */
   _si_trx_sdn_enable();  /* active high shutdown = reset */
 
-  for (int i = 0; i < 15; i++); /* a few microseconds */
+  for (int i = 0; i < 15; i++) { __NOP(); } /* a few microseconds */
 
   _si_trx_sdn_disable();   /* booting. expected to take 15ms */
 

firmware/src/watchdog.c

@@ -224,9 +224,9 @@ void WDT_Handler(void)
   /* Wait for the external watchdog to kill us */
   while (1) {
     led_on();
-    for (int i = 0; i < 25*1000; i++);
+    for (int i = 0; i < 25*1000; i++) { __NOP(); }
     led_off();
-    for (int i = 0; i < 25*1000; i++);
+    for (int i = 0; i < 25*1000; i++) { __NOP(); }
 
     /**
      * Whilst this is generally bad practice in this system we have an