minerva: Fix compatibility check for hekate main

Init now also returns status.

bootloader/mem/minerva.h

@@ -58,7 +58,7 @@ typedef enum
 } minerva_freq_t;
 
 void (*minerva_cfg)(mtc_config_t *mtc_cfg, void *);
-void minerva_init();
+u32  minerva_init();
 void minerva_change_freq(minerva_freq_t freq);
 void minerva_periodic_training();