Fix lockup when attempting to load a l0dable with disabled ELF loading

I addressed the issue reported in #228 (closed), but also did a bit more cleanup in related parts of the code. Check the individual commit messages for more details.

Fixes #228 (closed)

epicardium/api/control.c

@@ -227,6 +227,7 @@ void core1_wait_ready(void)
 		 * above loop, waiting for a new IVT.
 		 */
 		if (core1_info.ready) {
+			SEMA_FreeSema(_CONTROL_SEMAPHORE);
 			break;
 		}
 
@@ -245,6 +246,9 @@ void core1_wait_ready(void)
 
 void core1_load(void *ivt, char *args)
 {
+	while (SEMA_GetSema(_CONTROL_SEMAPHORE) == E_BUSY) {
+	}
+
 	/* If the core is currently in an API call, reset it. */
 	API_CALL_MEM->call_flag = _API_FLAG_IDLE;
 	API_CALL_MEM->id        = 0;